Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Oil and Gas Activities in Cook Inlet, Alaska, 37442-37506 [2019-15867]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 84, Number 147 (Wednesday, July 31, 2019)]
[Rules and Regulations]
[Pages 37442-37506]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2019-15867]



[[Page 37441]]

Vol. 84

Wednesday,

No. 147

July 31, 2019

Part III





Department of Commerce





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National Oceanic and Atmospheric Administration





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50 CFR Part 217





Takes of Marine Mammals Incidental to Specified Activities; Taking 
Marine Mammals Incidental to Oil and Gas Activities in Cook Inlet, 
Alaska; Final Rule

Federal Register / Vol. 84 , No. 147 / Wednesday, July 31, 2019 / 
Rules and Regulations

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 217

[Docket No. 190214112-9535-02]
RIN 0648-BI62


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to Oil and Gas Activities in Cook 
Inlet, Alaska

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

ACTION: Final rule; issuance of Letters of Authorization (LOA).

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SUMMARY: NMFS, upon request from Hilcorp Alaska LLC (Hilcorp), hereby 
issues regulations to govern the unintentional taking of marine mammals 
incidental to oil and gas activities in Cook Inlet, Alaska, over the 
course of five years (2019-2024). These regulations, which allow for 
the issuance of Letters of Authorization (LOA) for the incidental take 
of marine mammals during the described activities and specified 
timeframes, prescribe the permissible methods of taking and other means 
of effecting the least practicable adverse impact on marine mammal 
species or stocks and their habitat, as well as requirements pertaining 
to the monitoring and reporting of such taking. In accordance with the 
Marine Mammal Protection Act (MMPA), as amended, and implementing 
regulations, notification is hereby additionally given that a LOA has 
been issued to Hilcorp to take marine mammals incidental to oil and gas 
activities.

DATES: Effective from July 30, 2019, to July 30, 2024.

FOR FURTHER INFORMATION CONTACT: Sara Young, Office of Protected 
Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Availability

    A copy of Hilcorp's application and any supporting documents, as 
well as a list of the references cited in this document, may be 
obtained online at: www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act. In case of problems 
accessing these documents, please call the contact listed above (see 
FOR FURTHER INFORMATION CONTACT).

Purpose and Need for Regulatory Action

    These regulations establish a framework under the authority of the 
MMPA (16 U.S.C. 1361 et seq.) to allow for the authorization of take of 
marine mammals incidental to Hilcorp's oil and gas activities in Cook 
Inlet, Alaska.
    We received an application from Hilcorp requesting five-year 
regulations and authorization to take multiple species of marine 
mammals. Take will occur by Level A and Level B harassment incidental 
to a variety of sources including: Two-dimensional (2D) and three-
dimensional (3D) seismic surveys, geohazard surveys, vibratory sheet 
pile driving, and drilling of exploratory wells. Please see 
``Background'' below for definitions of harassment.

Legal Authority for the Action

    Section 101(a)(5)(A) of the MMPA (16 U.S.C. 1371(a)(5)(A)) directs 
the Secretary of Commerce to allow, upon request, the incidental, but 
not intentional taking of small numbers of marine mammals by U.S. 
citizens who engage in a specified activity (other than commercial 
fishing) within a specified geographical region for up to five years 
if, after notice and public comment, the agency makes certain findings 
and issues regulations that set forth permissible methods of taking 
pursuant to that activity and other means of effecting the least 
practicable adverse impact on the affected species or stocks and their 
habitat (see the discussion below in the ``Mitigation'' section), as 
well as monitoring and reporting requirements. Section 101(a)(5)(A) of 
the MMPA and the implementing regulations at 50 CFR part 216, subpart I 
provide the legal basis for issuing this rule containing five-year 
regulations, and for any subsequent LOAs. As directed by this legal 
authority, this rule contains mitigation, monitoring, and reporting 
requirements.

Summary of Major Provisions Within the Rule

    Following is a summary of the major provisions of this rule 
regarding Hilcorp's activities. These measures include:
     Required monitoring of the ensonified areas to detect the 
presence of marine mammals before beginning activities;
     Required aerial surveys to search for Cook Inlet beluga 
whales before beginning seismic surveys;
     Shutdown of activities under certain circumstances to 
minimize injury of marine mammals;
     Ramp up at the beginning of seismic surveying to allow 
marine mammals the opportunity to leave the area prior to beginning the 
survey at full power, and vessel strike avoidance;
     Ramp up of impact hammering of the drive pipe for the 
conductor pipe driven from the drill rig; and
     Ceasing noise producing activities within 10 miles (16 km) 
of the mean higher high water (MHHW) line of the Susitna Delta (Beluga 
River to the Little Susitna River) between April 15 and October 15, as 
well as ceasing seismic activity within the Level B harassment isopleth 
distance of the mouth of the Kasilof River between January 1 and May 
31.

Background

    The MMPA prohibits the ``take'' of marine mammals, with certain 
exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 
et seq.) direct the Secretary of Commerce (as delegated to NMFS) to 
allow, upon request, the incidental, but not intentional, taking of 
small numbers of marine mammals by U.S. citizens who engage in a 
specified activity (other than commercial fishing) within a specified 
geographical region if certain findings are made and either regulations 
are issued or, if the taking is limited to harassment, a notice of a 
proposed incidental take authorization may be provided to the public 
for review.
    Authorization for incidental takings shall be granted if NMFS finds 
that the taking will have a negligible impact on the species or 
stock(s) and will not have an unmitigable adverse impact on the 
availability of the species or stock(s) for taking for subsistence uses 
(where relevant). Further, NMFS must prescribe the permissible methods 
of taking and other means of effecting the least practicable adverse 
impact on the affected species or stocks and their habitat, paying 
particular attention to rookeries, mating grounds, and areas of similar 
significance, and on the availability of such species or stocks for 
taking for certain subsistence uses (referred to in shorthand as 
``mitigation''); and requirements pertaining to the mitigation, 
monitoring and reporting of such takings must be set forth.
    NMFS has defined ``negligible impact'' in 50 CFR 216.103 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.
    The MMPA states that the term ``take'' means to harass, hunt, 
capture, kill or attempt to harass, hunt, capture, or kill

[[Page 37443]]

any marine mammal. Except with respect to certain activities not 
pertinent here, the MMPA defines ``harassment'' as any act of pursuit, 
torment, or annoyance which (i) has the potential to injure a marine 
mammal or marine mammal stock in the wild (Level A harassment); or (ii) 
has the potential to disturb a marine mammal or marine mammal stock in 
the wild by causing disruption of behavioral patterns, including, but 
not limited to, migration, breathing, nursing, breeding, feeding, or 
sheltering (Level B harassment).

National Environmental Policy Act

    To comply with the National Environmental Policy Act of 1969 (NEPA; 
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A, 
NMFS reviewed our proposed action (i.e., the issuance of an incidental 
harassment authorization) with respect to potential impacts on the 
human environment.
    NMFS prepared an Environmental Assessment (EA) and analyzed the 
potential impacts to marine mammals that will result from Hilcorp's 
activities. A Finding of No Significant Impact (FONSI) was signed on 
July 17, 2019. A copy of the EA and FONSI is available at https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-oil-and-gas.

Summary of Request

    On April 17, 2018, NMFS received an application from Hilcorp (or 
``the applicant'') requesting authorization to incidentally take marine 
mammals, by Level A and Level B harassment, incidental to noise 
exposure resulting from oil and gas activities in Cook Inlet, Alaska, 
from May 2019 to April 2024. These regulations will be valid for a 
period of five years. On October 8, 2018, NMFS deemed the application 
adequate and complete.
    The use of sound sources such as those described in the application 
(e.g., seismic airguns) may result in the take of marine mammals 
through disruption of behavioral patterns or may cause auditory injury 
of marine mammals. Therefore, incidental take authorization under the 
MMPA is warranted.

Description of Activity

Overview

    The scope of Hilcorp's Incidental Take Regulations (ITR) Petition 
includes four stages of activity, including exploration, development, 
production, and decommissioning activities within the applicant's area 
of operations in and adjacent to Cook Inlet within the Petition's 
geographic area (Figures 3 and 8 in the application). Table 1 
summarizes the planned activities within the geographic scope of this 
Petition, and the following text describes these activities in more 
detail. This section is organized into two primary areas within Cook 
Inlet: Lower Cook Inlet (south of the Forelands to Homer) and middle 
Cook Inlet (north of the Forelands to Susitna/Point Possession).

                              Table 1--Summary of Planned Activities Included in Incidental Take Regulations (ITR) Petition
                                            [Updates from Table 1 in the proposed rule are reflected in bold]
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                                                                                                                    Anticipated       Antiicpated noise
           Project name              Cook Inlet region      Year(s) planned             Seasonal timing               duration             sources
--------------------------------------------------------------------------------------------------------------------------------------------------------
Anchor Point 2D seismic survey...  Lower Cook Inlet,     2021 or 2022.........  April-October.................  30 days (10 days     Marine: 1 source
                                    Anchor Point to                                                              seismic).            vessel with airgun
                                    Kasilof.                                                                                          array, 1 node
                                                                                                                                      vessel.
                                                                                                                                     Onshore/Intertidal:
                                                                                                                                      Shot holes,
                                                                                                                                      tracked vehicles,
                                                                                                                                      helicopters.
OCS 3D seismic survey............  Lower Cook Inlet OCS  2019 or 2020.........  April-October.................  45-60 days.........  1 source vessel
                                                                                                                                      with airgun array,
                                                                                                                                      2 support vessels,
                                                                                                                                      1 mitigation
                                                                                                                                      vessel.
OCS geohazard survey.............  Lower Cook Inlet OCS  2020-2021............  April-October.................  30 days............  1 vessel with
                                                                                                                                      echosounders and/
                                                                                                                                      or sub-bottom
                                                                                                                                      profilers.
OCS exploratory wells............  Lower Cook Inlet OCS  2020-2022............  February-November.............  40-60 days per       1 jack-up rig,
                                                                                                                 well, 2-4 wells      drive pipe
                                                                                                                 per year.            installation,
                                                                                                                                      vertical seismic
                                                                                                                                      profiling, 2-3
                                                                                                                                      tugs for towing
                                                                                                                                      rig, support
                                                                                                                                      vessels,
                                                                                                                                      helicopters.
Iniskin Peninsula exploration and  Lower Cook Inlet,     2020-2022............  April-October.................  180 days each year.  Construction of
 development (causeway              west side.                                                                                        causeway,
 construction).                                                                                                                       vibratory sheet
                                                                                                                                      pile driving,
                                                                                                                                      dredging, vessels.
Platform & pipeline maintenance..  Middle Cook Inlet...  2019-2024............  April-October.................  180 days (each       Vessels, water
                                                                                                                 year).               jets, hydraulic
                                                                                                                                      grinders, pingers,
                                                                                                                                      helicopters, and/
                                                                                                                                      or sub-bottom
                                                                                                                                      profilers No
                                                                                                                                      change.
North Cook Inlet Unit subsea well  Middle Cook Inlet...  2020.................  April-October.................  14 days............  1 vessel with
 geohazard survey.                                                                                                                    echosounders and/
                                                                                                                                      or sub-bottom
                                                                                                                                      profilers No
                                                                                                                                      change.
North Cook Inlet Unit well         Middle Cook Inlet...  2020.................  April-October.................  90 days............  1 jack-up rig, tugs
 abandonment activity.                                                                                                                towing rig,
                                                                                                                                      support vessel,
                                                                                                                                      helicopters.
Trading Bay area geohazard survey  Middle Cook Inlet...  2020.................  April-October.................  30 days............  1 vessel with
                                                                                                                                      echosounders and/
                                                                                                                                      or sub-bottom
                                                                                                                                      profilers.

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Trading Bay area exploratory       Middle Cook Inlet...  2020.................  April-October.................  120-150 days.......  1 jack-up rig,
 wells.                                                                                                                               drive pipe
                                                                                                                                      installation,
                                                                                                                                      vertical seismic
                                                                                                                                      profiling, tugs
                                                                                                                                      towing rig,
                                                                                                                                      support vessel,
                                                                                                                                      helicopters.
Granite Point production drilling  Middle Cook Inlet...  2019.................  June-October..................  120-150 days.......  1 jack-up rig, tugs
 and geohazard survey *.                                                                                                              towing rig,
                                                                                                                                      support vessel,
                                                                                                                                      helicopters, 1
                                                                                                                                      vessel with
                                                                                                                                      echosounders.
Drift River terminal               Lower Cook Inlet,     2020-2023............  April-October.................  120 days...........  Vessels.
 decommissioning.                   west side.
--------------------------------------------------------------------------------------------------------------------------------------------------------
* While these activities were added after the proposed rule, they do not involve technologies that NMFS believes are likely to result in take and
  therefore do not change the number of takes authorized.
Bold text indicates changes from Table 1 in the Proposed Rule.

Dates and Duration

    The scope of the Petition includes exploration, development, 
production, and decommissioning activities within the applicant's area 
of operations in and adjacent to Cook Inlet within the Petition's 
geographic area (Figures 3 and 8 in the application) for the period of 
five years beginning May 1, 2019, extending through April 30, 2024.

Specific Geographic Region

    The geographic area of activity covers a total of approximately 2.7 
million acres (10,926 km\2\) in Cook Inlet. It includes land and 
adjacent waters in Cook Inlet including both State of Alaska and 
Federal OCS waters (Figure 3 and 8 in the application). The area 
extends from the north at the Susitna Delta on the west side 
(61[deg]10'48 N, 151[deg]0'55 W) and Point Possession on the east side 
(61[deg]2'11 N, 150[deg]23'30 W) to the south at Ursus Cove on the west 
side (59[deg]26'20 N, 153[deg]45'5 W) and Nanwalek on the east side 
(59[deg]24'5 N, 151[deg]56'30 W). The area is depicted in Figures 3 and 
8 of the application.

Detailed Description of Specific Activity

    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 some uncertainty 
in the timing, duration, and complete scope of work for each year. The 
applicant will submit an application for a LOA with the specific 
details of the planned work for that year and with estimated take 
numbers using the same assumptions as in the ITR Petition.
Activities in Lower Cook Inlet
    Based on potential future lease sales in both State and Federal 
waters, operators collect two-dimensional (2D) seismic data to 
determine the location of possible oil and gas prospects. Generally, 2D 
survey lines are spaced farther apart than three-dimensional (3D) 
survey lines, and 2D surveys are conducted in a regional pattern that 
provides less detailed geological information. 2D surveys are used to 
cover wider areas to map geologic structures on a regional scale. 
Airgun array sizes used during 2D surveys are similar to those used 
during 3D surveys.
Activities in Middle Cook Inlet
2D Seismic Survey
    During the timeframe of this Petition, the region of interest for 
the 2D survey is the marine, intertidal, and onshore area on the 
eastern side of Cook Inlet from Anchor Point to the mouth of the 
Kasilof River. The area of interest is approximately 8 km (5 miles) 
offshore of the coastline. The anticipated timing of the planned 2D 
survey is in the open water season (April through October) in either 
2020 or 2021. The actual survey duration is approximately 30 days in 
either year, but only 10 of the 30 days would be in-water seismic work.
    The 2D seismic data are acquired using airguns in the marine zone, 
airguns in the intertidal zone when the tide is high, drilled shot 
holes in the intertidal zone when the tide is low, and drilled shot 
holes in the land zone. The data are recorded using an autonomous nodal 
system (i.e., no cables) that are deployed in the marine, intertidal, 
and land zones. The planned source lines (airgun and shot holes) are 
approximately 16 km (10 mi) in length running perpendicular to the 
coastline (see Figure 1 in the application). The source lines are 
spaced every 8 km (5 mi) in between Anchor Point and Kasilof, with 
approximately 9-10 lines over the area of interest.
    In the marine and high tide intertidal zones, data will be acquired 
using a shallow water airgun towed behind one source vessel. Although 
the precise volume of the airgun array is unknown at this time, Hilcorp 
will use an airgun array similar to what has been used for surveys in 
Cook Inlet by Apache (2011-2013) and SAExploration (2015): Either a 
2,400 cubic inch (in\3\) or 1,760 in\3\ array. A 2,400 in\3\ airgun was 
assumed for analysis in this rule to be conservative in take 
estimation. In addition, the source vessel will be equipped with a 440 
in\3\ shallow water source which it can deploy at high tide in the 
intertidal area in less than 1.8 meters (m) (6 feet (ft)) of water. 
Source lines are oriented along the node line. A single vessel is 
capable of acquiring a source line in approximately 1-2 hours (hrs). In 
general, only one source line will be collected in one day to allow for 
all the node deployments and retrievals, and intertidal and land zone 
shot holes drilling. There are up to 10 source lines, so if all 
operations run smoothly, there will only be 2 hrs per day over 10 days 
of airgun activity. Hilcorp anticipates the entire operation to take 
approximately 30 days to complete to account for weather and equipment 
contingencies.
    The recording system that will be employed is an autonomous system 
``nodal'' (i.e., no cables), which is expected to be made up of at 
least two types of nodes; one for the land and one for the intertidal 
and marine environment. For the intertidal and marine zone, this will 
be a submersible multi-component system made up of three velocity 
sensors and a hydrophone. These systems have the ability to record 
continuous data. Inline

[[Page 37445]]

receiver intervals for the node systems are approximately 50 m (165 
ft). For 2D seismic surveys, the nodes are deployed along the same line 
as the seismic source. The deployment length is restricted by battery 
duration and data storage capacity. The marine nodes will be placed 
using one node vessel. The vessels required for the 2D seismic survey 
include just a source vessel and a node vessel that is conducting only 
passive recording.
    In the marine environment, once the nodes are placed on the 
seafloor, the exact position of each node is required. In very shallow 
water, the node positions are either surveyed by a land surveyor when 
the tide is low, or the position is accepted based on the position at 
which the navigator has laid the unit. In deeper water, a hull or pole 
mounted pinger to send a signal to the transponder attached to each 
node will be used. The transponders are coded and the crew knows which 
transponder goes with which node prior to the layout. The transponders 
response (once pinged) is added together with several other responses 
to create a suite of range and bearing between the pinger boat and the 
node. Those data are then calculated to precisely position the node. In 
good conditions, the nodes can be interrogated as they are laid out. It 
is also common for the nodes to be pinged after they have been laid 
out. Onshore and intertidal locating of source and receivers will be 
accomplished with Differential Global Positioning System/roving units 
(DGPS/RTK) equipped with telemetry radios which will be linked to a 
base station established on the source vessel. Survey crews will have 
both helicopter and light tracked vehicle support. Offshore source and 
receivers will be positioned with an integrated navigation system (INS) 
utilizing DGPS/RTK links to the land base stations. The integrated 
navigation system will be capable of many features that are critical to 
efficient safe operations. The system will include a hazard display 
system that can be loaded with known obstructions, or exclusion zones.
    Apache conducted a sound source verification (SSV) for the 440 
in\3\ and 2,400 in\3\ arrays in 2012 (Austin and Warner 2012; 81 FR 
47239). The location of the SSV was in Beshta Bay on the western side 
of Cook Inlet (between Granite Point and North Forelands). Water depths 
ranged from 30-70 m (98-229 ft).
    For the 440 in\3\ array, the measured levels for the broadside 
direction were 217 decibel (dB) re: 1microPa ([mu]Pa) peak, 190 dB 
sound exposure level (SEL), and 201 dB root mean square (rms) at a 
distance of 50 m. The estimated distance to the 160 dB rms (90th 
percentile) threshold, assuming the empirically measured transmission 
loss of 20.4 log R (Austin and Warner, 2012), was 2,500 m. Sound levels 
near the source were highest between 30 and 300 hertz (Hz) in the 
endfire direction and between 20 Hz and 300 Hz in the broadside 
direction.
    For the 2,400 in\3\ array, the measured levels for the endfire 
direction were 217 dB peak, 185 dB SEL, and 197 dB rms at a distance of 
100 m. The estimated distance to the 160 dB rms (90th percentile) 
thresholds, assuming the empirically measured transmission loss of 16.9 
log R, was 7,770 m. Sound levels near the source were highest between 
30 and 150 Hz in the endfire direction and between 50 and 200 Hz in the 
broadside direction. During the process of issuing regulations for 
Apache Alaska, JASCO provided an updated distance of 7,330 m for a 24-
hour survey (81 FR 47239). This updated estimate is considered the best 
available science for seismic activity of similar array size in Cook 
Inlet and was used to estimate take in this rulemaking. It is important 
to note that neither survey by Hilcorp is expected to use an airgun 
array of 2,400 in\3\; both surveys will use an airgun array with a 
lower in\3\ than this. However, 7,330 m is used in calculations as it 
is the closest known and measured value for seismic airgun isopleths 
for arrays of a similar size in middle and lower Cook Inlet. Further, a 
sound source verification (SSV) will be performed to characterize the 
actual array and environmental parameters for the area to be surveyed. 
These measured levels were used to evaluate potential Level A 
harassment (217 dB peak and 185 dB SEL at 100 m assuming 15 log 
transmission loss) and Level B harassment (7,330 m distance to 160 dB 
threshold) isopleths from these sound sources (see Estimated Take 
section).
3D Seismic Survey
    During the timeframe of this Petition, Hilcorp plans to collect 3D 
seismic data for approximately 45-60 days starting May 1, 2019 over 8 
of the 14 OCS lease blocks in lower Cook Inlet. The 3D seismic survey 
is comprised of an area of approximately 790 km\2\ (305 mi\2\) through 
8 lease blocks (6357, 6405, 6406, 6407, 6455, 6456, 6457, 6458). 
Hilcorp submitted an application for an Incidental Harassment 
Authorization (IHA) in late 2017 for a planned survey in 2018 but 
withdrew the application, and now plans for the survey to take place in 
2019 and cover several years of surveying and development. Hilcorp 
plans to collect 3D seismic data for approximately 45-60 days in either 
the fall of 2019 (September-October) or spring of 2020 (April-May). 
Hilcorp plans to collect the seismic survey data in one season (either 
fall 2019 or spring 2020). If the seismic vessel is not able to start 
in September and end by October 31 to comply with BOEM lease 
stipulations, the survey will be postponed until spring 2020. The 
length of the survey will depend on weather, equipment, and marine 
mammal delays (contingencies of 20 percent weather, 10 percent 
equipment, 10 percent marine mammal were assumed in this analysis, or a 
40 percent increase in expected duration to account for the 
aforementioned delays).
    Polarcus is the intended seismic contractor, and the general 
seismic survey design is provided below. The 3D seismic data will be 
acquired using a specially designed marine seismic vessel towing 
between 8 and 12 ~2,400-m (1.5 mi) recording cables with a dual air gun 
array. The survey will involve one source vessel, one support vessel, 
one chase vessel, and one mitigation vessel. The anticipated seismic 
source to be deployed from the source vessel is a 14-airgun array with 
a total volume of 1,945 in\3\. Crew changes are expected to occur every 
four to six weeks using a helicopter or support vessel from shore bases 
in lower Cook Inlet. The seismic survey will be active 24 hrs per day. 
The array will be towed at a speed of approximately 7.41 km/hr (4 
knots), with seismic data collected continuously. Data acquisition will 
occur for approximately 5 hrs, followed by a 1.5-hr period to turn and 
reposition the vessel for another pass. The turn radius on the seismic 
vessel is approximately 3,200 m (2 mi).
    The data acquisition will be shot parallel to the Cook Inlet 
shorelines in a north/south direction. This operational direction will 
keep recording equipment/streamers in line with Cook Inlet currents and 
tides and keep the equipment away from shallow waters on the east and 
west sides. The program may be modified if the survey cannot be 
conducted as a result of noise conditions onsite (i.e., ambient noise). 
The airguns will typically be turned off during the turns. The vessel 
will turn into the tides to ensure the recording cables/streamers 
remain in line behind the vessel.
    Hilcorp plans to use an array that provides for the lowest possible 
sound source to collect the target data. The array is a Bolt 1900 LLXT 
dual gun array. The airguns will be configured as two linear arrays or 
``strings;'' each string will have 7 airguns shooting in a ``flip-
flop'' configuration for a total of 14 airguns. The airguns will range 
in

[[Page 37446]]

volume from 45 to 290 in\3\ for a total of 1,945 in\3\. The first and 
last are spaced approximately 14 m (45.9 ft) apart and the strings are 
separated by approximately 10 m (32.8 ft). The two airgun strings will 
be distributed across an approximate area of 30 x 14 m (98.4 x 45.9 ft) 
behind the source vessel and will be towed 300-400 m (984-1,312 ft) 
behind the vessel at a depth of 5 m (16.4 ft). The firing pressure of 
the array is 2,000 pounds per square inch (psi). The airgun will fire 
every 4.5 to 6 seconds, depending on the exact speed of the vessel. 
When fired, a brief (25 milliseconds [ms] to 140 ms) pulse of sound is 
emitted by all airguns nearly simultaneously.
    Hilcorp intends to use 8 Sercel-type solid streamers or 
functionally similar for recording the seismic data (Figure 5 in the 
application). Each streamer will be approximately 2,400 m (150 mi) in 
length and will be towed approximately 8-15 m (26.2-49.2 ft) or deeper 
below the surface of the water. The streamers will be placed 
approximately 50 m (165 ft) apart to provide a total streamer spread of 
400 m (1,148 ft). Hilcorp recognizes solid streamers as best in class 
for marine data acquisition because of unmatched reliability, signal to 
noise ratio, low frequency content, and noise immunity.
    The survey will involve one source vessel, one support vessel, one 
or two chase vessels, and one mitigation vessel. The source vessel tows 
the airgun array and the streamers. The support vessel provides general 
support for the source vessel, including supplies, crew changes, etc. 
The chase vessel monitors the in-water equipment and maintains a 
security perimeter around the streamers. The mitigation vessel provides 
a viewing platform to augment the marine mammal monitoring program.
    The planned volume of the airgun array is 1,945 in\3\. Hilcorp and 
their partners will be conducting detailed modeling of the array 
output, but a detailed SSV has not been conducted for this array in 
Cook Inlet. Therefore, for the purposes of estimating acoustic 
harassment, results from previous seismic surveys in Cook Inlet by 
Apache and SAExploration, particularly the 2,400 in\3\ array, were 
used. Apache conducted an SSV for the 440 in\3\ and 2,400 in\3\ arrays 
in 2012 (Austin and Warner 2012; 81 FR 47239). The location of the SSV 
was in Beshta Bay on the western side of Cook Inlet (between Granite 
Point and North Forelands). Water depths ranged from 30-70 m (98-229 
ft). For the 2,400 in\3\ array, the measured levels for the endfire 
direction were 217 dB peak, 185 dB SEL, and 197 dB rms at a distance of 
100 m. The estimated distance to the 160 dB rms (90th percentile) 
thresholds, assuming the empirically measured transmission loss of 16.9 
log R, was 7,770 m. Sound levels near the source were highest between 
30 and 150 Hz in the endfire direction and between 50 and 200 Hz in the 
broadside direction.
    These measured levels were used to evaluate potential Level A (217 
dB peak and 185 dB SEL at 100 m assuming 15 log transmission loss) and 
Level B (7,330 m distance to 160 dB threshold) acoustic harassment of 
marine mammals in this Petition.
Geohazard and Geotechnical Surveys
    Upon completion of the 3D seismic survey over the lower Cook Inlet 
OCS leases, Hilcorp plans to conduct a geohazard survey on site-
specific regions within the area of interest prior to conducting 
exploratory drilling. The precise location is not known, as it depends 
on the results of the 3D seismic survey, but the location will be 
within the lease blocks. The anticipated timing of the activity is in 
either the fall of 2019 or the spring of 2020. The actual survey 
duration will take approximately 30 days.
    The suite of equipment used during a typical geohazards survey 
consists of single beam and multi-beam echosounders, which provide 
water depths and seafloor morphology; a side scan sonar that provides 
acoustic images of the seafloor; a sub-bottom profiler which provides 
20 to 200 m (66 to 656 ft) sub-seafloor penetration with a 6- to 20-
centimeter (cm, 2.4-7.9-inch (in)) resolution. Magnetometers, to detect 
ferrous items, may also be used. Geotechnical surveys are conducted to 
collect bottom samples to obtain physical and chemical data on surface 
and near sub-surface sediments. Sediment samples typically are 
collected using a gravity/piston corer or grab sampler. The surveys are 
conducted from a single support vessel.
    The echosounders and sub-bottom profilers are generally hull-
mounted or towed behind a single vessel. The ship travels at 3-4.5 
knots (5.6-8.3 km/hr). Surveys are site specific and can cover less 
than one lease block in a day, but the survey extent is determined by 
the number of potential drill sites in an area. BOEM guidelines at NTL-
A01 require data to be gathered on a 150 by 300 m (492 by 984 ft) grid 
within 600 m (1,969 ft) of the surface location of the drill site, a 
300 by 600 m (984 by 1,969 ft) grid along the wellbore path out to 
1,200 m (3,937 ft) beyond the surface projection of the conductor 
casing, and extending an additional 1,200 m beyond that limit with a 
1,200 by 1,200 m grid out to 2,400 m (7,874 ft) from the well site.
    The multibeam echosounder, single beam echosounder, and side scan 
sonar operate at frequencies of greater than 200 kHz. Based on the 
frequency ranges of these pieces of equipment and the hearing ranges of 
the marine mammals that have the potential to occur in the action area, 
the noise produced by the echosounders and side scan sonar are not 
likely to result in take of marine mammals and are not considered 
further in this document.
    The geophysical surveys include use of a low resolution and high 
resolution sub-bottom profiler. The high-resolution sub-bottom profiler 
operates at source level of 210 dB re 1 [mu]Pa RMS at 1 m. The system 
emits energy in the frequency bands of 2 to 24 kHz. The beam width is 
15 to 24 degrees. Typical pulse rate is between 3 and 10 Hz. The 
secondary low-resolution sub-bottom profiler will be utilized as 
necessary to increase sub-bottom profile penetration. The system emits 
energy in the frequency bands of 1 to 4 kHz.
Exploratory Drilling
    Operators will drill exploratory wells based on mapping of 
subsurface structures using 2D and 3D seismic data and historical well 
information. Hilcorp plans to conduct the exploratory drilling program 
April to October between 2020 and 2022. The exact start date is 
currently unknown and is dependent on the results of the seismic 
survey, geohazard survey, and scheduling availability of the drill rig. 
It is expected that each well will take approximately 40-60 days to 
drill and test. Beginning in spring 2020, Hilcorp Alaska plans to 
possibly drill two and as many as four exploratory wells, pending 
results of the 3D seismic survey in the lower Cook Inlet OCS leases. 
After testing, the wells may be plugged and abandoned.
    Hilcorp Alaska plans to conduct its exploratory drilling using a 
rig similar to the Spartan 151 drill rig. The Spartan 151 is a 150 H 
class independent leg, cantilevered jack-up drill rig with a drilling 
depth capability of 7,620 m (25,000 ft) that can operate in maximum 
water depths up to 46 m (150 ft). Depending on the rig selection and 
location, the drilling rig will be towed on site using up to three 
ocean-going tugs licensed to operate in Cook Inlet. Rig moves will be 
conducted in a manner to minimize any potential risk regarding safety 
as well as cultural or environmental impact. While under tow to the 
well sites, rig operations will be monitored by Hilcorp and the 
drilling contractor management. Very High Frequency (VHF) radio, 
satellite, and

[[Page 37447]]

cellular phone communication systems will be used while the rig is 
under tow. Helicopter transport will also be available.
    Similarly to transiting vessels, although some marine mammals could 
receive sound levels in exceedance of the general acoustic threshold of 
120 dB from the tugs towing the drill rig during this project, take is 
unlikely to occur, primarily because of the predictable movement of 
vessels and tugs. Additionally, marine mammal population density in the 
project area is low (see Estimated Take section below), and those that 
are present are likely habituated to the existing baseline of 
commercial ship traffic. Further, there are no activity-, location-, or 
species-specific circumstances or other contextual factors that 
increase concern and the likelihood of take from towing of the drill 
rig.
    The drilling program for the well will be described in detail in an 
Exploration Plan to BOEM. The Exploration Plan will present information 
on the drilling mud program; casing design, formation evaluation 
program; cementing programs; and other engineering information. After 
rig up/rig acceptance by Hilcorp Alaska, the wells will be spudded and 
drilled to bottom-hole depths of approximately 2,100 to 4,900 m (7,000 
to 16,000 ft) depending on the well. It is expected that each well will 
take about 40-60 days to drill and up to 10-21 days of well testing. If 
two wells are drilled, it will take approximately 80-120 days to 
complete the full program; if four wells are drilled, it will take 
approximately 160-240 days to complete the full program.
    Primary sources of rig-based acoustic energy were identified as 
coming from the D399/D398 diesel engines, the PZ-10 mud pump, 
ventilation fans (and associated exhaust), and electrical generators. 
The source level of one of the strongest acoustic sources, the diesel 
engines, was estimated to be 137 dB re 1 [mu]Pa rms at 1 m in the 141-
178 Hz bandwidth. Based on this measured level, the 120 dB rms acoustic 
received level isopleth is 50 m (154 ft) away from where the energy 
enters the water (jack-up leg or drill riser). Drilling and well 
construction sounds are similar to vessel sounds in that they are 
relatively low-level and low-frequency. Since the rig is stationary in 
a location with low marine mammal density, the impact of drilling and 
well construction sounds produced from the jack up rig is expected to 
be lower than a typical large vessel. There is open water in all 
directions from the drilling location. Any marine mammal approaching 
the rig would be fully aware of its presence long before approaching or 
entering the zone of influence for behavioral harassment, and we are 
unaware of any specifically important habitat features (e.g., 
concentrations of prey or refuge from predators) within the rig's zone 
of influence that encourages marine mammal use and exposure to higher 
levels of noise closer to the source. Given the absence of any 
activity-, location-, or species-specific circumstances or other 
contextual factors that increase concern, we do not expect routine 
drilling noise to result in the take of marine mammals.
    When planned and permitted operations are completed, the well will 
be suspended according to Bureau of Safety and Environmental 
Enforcement (BSEE) regulations. The well casings will be landed in a 
mudline hanger after each hole section is drilled. When the well is 
abandoned, the production casing is sealed with mechanical plugging 
devices and cement to prevent the movement of any reservoir fluids 
between various strata. Each casing string will be cutoff below the 
surface and sealed with a cement plug. A final shallow cement plug will 
be set to approximately 3.05 m (10 ft) below the mudline. At this 
point, the surface casing, conductor, and drive pipe will be cutoff and 
the three cutoff casings and the mudline hanger are pulled to the deck 
of the jack-up rig for final disposal. The plugging and abandonment 
procedures are part of the Well Plan which is reviewed by BSEE prior to 
being issued an approved Permit to Drill.
    A drive pipe is a relatively short, large-diameter pipe driven into 
the sediment prior to the drilling of oil wells. The drive pipe serves 
to support the initial sedimentary part of the well, preventing the 
looser surface layer from collapsing and obstructing the wellbore. 
Drive pipes are installed using pile driving techniques. Hilcorp plans 
to drive approximately 60 m of 76.2-cm pipe at each well site prior to 
drilling using a Delmar D62-22 impact hammer (or similar). This hammer 
has an impact weight of 6,200 kg (13,640 lbs). The drive pipe driving 
event is expected to last one to three days at each well site, although 
actual pounding of the pipe will only occur intermittently during this 
period.
    Illingworth & Rodkin (2014) measured the hammer noise for hammering 
the drive pipe operating from the rig Endeavour for Buccaneer in 2013 
and reported the source level at 190 dB at 55 m, with underwater levels 
exceeding 160 dB rms threshold at 1.63 km (1 mi). The measured sound 
levels for the pipe driving were used to evaluate potential Level A 
(source level of 221dB @ 1m and assuming 15 logR transmission loss) and 
Level B (1,630 m distance to the 160 dB threshold) acoustic harassment 
of marine mammals. Conductors are slightly smaller diameter pipes than 
the drive pipes used to transport or ``conduct'' drill cuttings to the 
surface. For these wells, a 50.8-cm (20-in) conductor pipe may be 
drilled, not hammered, inside the drive pipe, dependent on the 
integrity of surface formations. There are no noise concerns associated 
with the conductor pipe drilling.
    Once the well is drilled, accurate follow-up seismic data may be 
collected by placing a receiver at known depths in the borehole and 
shooting a seismic airgun at the surface near the borehole, called 
vertical seismic profiling (VSP). These data provide high-resolution 
images of the geological layers penetrated by the borehole and can be 
used to accurately correlate original surface seismic data. The actual 
size of the airgun array is not determined until the final well depth 
is known, but typical airgun array volumes are between 600 and 880 
in\3\. VSP typically takes less than two full days at each well site. 
Illingworth & Rodkin (2014) measured a 720 in\3\ array for Buccaneer in 
2013 and report the source level at 227 dB at 1 m, with underwater 
levels exceeding 160 dB rms threshold at 2.47 km (1.54 mi). The 
measured sound levels for the VSP were used to evaluate potential Level 
A harassment (227 dB rms at 1 m assuming 15 logR transmission loss) and 
Level B harassment (2,470 m distance to the 160 dB threshold) 
isopleths.
Iniskin Peninsula Exploration
    Hilcorp Alaska initiated baseline exploratory data collection in 
2013 for a proposed land-based oil and gas exploration and development 
project on the Iniskin Peninsula of Alaska, near Chinitna Bay. The 
project is approximately 97 km (60 mi) west of Homer on the west side 
of Cook Inlet in the Fitz Creek drainage. New project infrastructure 
includes material sites, a 6.9 km (4.3 mi) long access road, 
prefabricated bridges to cross four streams, an air strip, barge 
landing/staging areas, fuel storage facilities, water wells and 
extraction sites, an intertidal causeway, a camp/staging area, and a 
drill pad. Construction is anticipated to start in 2020.
    An intertidal rock causeway will be constructed adjacent to the 
Fitz Creek staging area to improve the accessibility of the barge 
landing during construction and drilling operations. The causeway will 
extend seaward from the high tide

[[Page 37448]]

line approximately 366 m (1,200 ft) to a landing area 46 m (150 ft) 
wide. A dock face will be constructed around the rock causeway so that 
barges will be able to dock along the causeway. Rock placement for the 
causeway is not known to generate sound at levels expected to disturb 
marine mammals. The causeway is also not planned at a known pinniped 
haulout or other biologically significant location for local marine 
mammals. Therefore, rock laying for the causeway is not considered 
further in this document.
    The causeway will need to be 75 percent built before the 
construction of the dock face will start. The dock face will be 
constructed with 18-m (60-ft) tall Z-sheet piles, all installed using a 
vibratory hammer. It will take approximately 14-25 days, depending on 
the length of the work shift, assuming approximately 25 percent of the 
day actual pile driving. The timing of pile driving will be in late 
summer or early winter, after the causeway has been partially 
constructed. Illingworth & Rodkin (2007) compiled measured near-source 
(10 m [32.8 ft]) SPL data from vibratory pile driving for different 
pile sizes ranging in diameter from 30.5 to 243.8 cm (12 to 96 in). For 
this Petition, the source level of the 61.0-cm (24-in) AZ steel sheet 
pile from Illingworth & Rodkin (2007) was used for the sheet pile. The 
measured sound levels of 160 dB rms at 10 m, assuming 15 logR 
transmission loss for the vibratory sheet pile driving, was used to 
evaluate potential Level A and B harassment isopleths. Airborne sound 
from this construction is only expected to impact pinnipeds that are 
hauled out in the area where sound levels exceed in-air harassment 
thresholds. While harbor seals are known to use nearby bays, no major 
land haulouts exist in the project area and no harassment from airborne 
sound is expected to result from project activities. Therefore, above-
water construction will not be discussed further in this document.
Activities in Middle Cook Inlet
Offshore Production Platforms
    Of the 17 production platforms in central Cook Inlet, 15 are owned 
by Hilcorp.
    Hilcorp performs routine construction on their platforms, depending 
on needs of the operations. Construction activities may take place up 
to 24 hrs a day. In-water activities include support vessels bringing 
supplies five days a week up to two trips per day between offshore 
systems at Kenai (OSK) and the platform. Depending on the needs, there 
may also be barges towed by tugs with equipment and helicopters for 
crew and supply changes. Routine supply-related transits from vessels 
and helicopters are not substantially different from routine vessel and 
air traffic already occurring in Cook Inlet, and take is not expected 
to occur from these activities.
Offshore Production Drilling
    Hilcorp routinely conducts development drilling activities at 
offshore platforms on a regular basis to meet the asset's production 
needs. Development drilling activities occurs from existing platforms 
within the Cook Inlet through either open well slots or existing 
wellbores in existing platform legs. Drilling activities from platforms 
within Cook Inlet are accomplished by using conventional drilling 
equipment from a variety of rig configurations.
    Some other platforms in Cook inlet have permanent drilling rigs 
installed that operate under power provided by the platform power 
generation systems, while others do not have drill rigs, and the use of 
a mobile drill rig is required. Mobile offshore drill rigs may be 
powered by the platform power generation (if compatible with the 
platform power system) or self-generate power with the use of diesel 
fired generators. For the reasons outlined above for the Lower Inlet, 
noise from routine drilling is not considered further in this document.
    Helicopter logistics for development drilling programs operations 
will include transportation for personnel and supplies. The helicopter 
support will be managed through existing offshore services based at the 
OSK Heliport to support rig crew changes and cargo handling. Helicopter 
flights to and from the platform while drilling is occurring is 
anticipated to increase (on average) by two flights per day from normal 
platform operations.
    Major supplies will be staged on-shore at the OSK Dock in Nikiski. 
Required supplies and equipment will be moved from the staging area to 
the platform in which drilling occurring by existing supply vessels 
that are currently in use supporting offshore operations within Cook 
Inlet. Vessel trips to and from the platform while drilling is 
occurring is anticipated to increase (on average) by two trips per day 
from normal platform operations. During mobile drill rig mobilization 
and demobilization, one support vessel is used continuously for 
approximately 30 days to facilitate moving rig equipment and materials.
Oil and Gas Pipeline Maintenance
    Each year, Hilcorp Alaska must verify the structural integrity of 
their platforms and pipelines located within Cook Inlet. Routine 
maintenance activities include: Subsea pipeline inspections, 
stabilizations, and repairs; platform leg inspections and repairs; and 
anode sled installations and/or replacement. In general, pipeline 
stabilization and pipeline repair are anticipated to occur in 
succession for a total of 6-10 weeks. However, if a pipeline 
stabilization location also requires repair, the divers will repair the 
pipeline at the same time they are stabilizing it. Pipeline repair 
activities are only to be conducted on an as-needed basis whereas 
pipeline stabilization activities will occur annually. During 
underwater inspections, if the divers identify an area of the pipeline 
that requires stabilization, they will place Sea-Crete bags at that 
time rather than waiting until the major pipeline stabilization effort 
that occurs later in the season.
    Natural gas and oil pipelines located on the seafloor of the Cook 
Inlet are inspected on an annual basis using ultrasonic testing (UT), 
cathodic protection surveys, multi-beam sonar surveys, and sub-bottom 
profilers. Deficiencies identified are corrected using pipeline 
stabilization methods or USDOT-approved pipeline repair techniques. The 
applicant employs dive teams to conduct physical inspections and 
evaluate cathodic protection status and thickness of subsea pipelines 
on an annual basis. If required for accurate measurements, divers may 
use a water jet to provide visual access to the pipeline. For 
stabilization, inspection dive teams may place Sea-Crete bags beneath 
the pipeline to replace any materials removed by the water jet. Results 
of the inspections are recorded and significant deficiencies are noted 
for repair.
    Multi-beam sonar and sub-bottom profilers may also be used to 
obtain images of the seabed along and immediately adjacent to all 
subsea pipelines. Elements of pipeline inspections that could produce 
underwater noise include: The dive support vessel, water jet, multi-
beam sonar/sub-bottom profiler and accompanying vessel.
    A water jet is a zero-thrust water compressor that is used for 
underwater removal of marine growth or rock debris underneath the 
pipeline. The system operates through a mobile pump which draws water 
from the location of the work. Water jets likely to be used in Cook 
Inlet include, but are not limited to, the CaviDyne CaviBlaster[supreg] 
and the Gardner Denver Liqua-Blaster. Noise generated during the use of 
the water jets is very short in duration (30 minutes

[[Page 37449]]

or less at any given time) and intermittent.
    Hilcorp Alaska conducted underwater measurements during 13 minutes 
of CaviBlaster[supreg] use in Cook Inlet in April 2017 (Austin 2017). 
Received sound levels were measured up to 143 dB re 1 [mu]Pa rms at 170 
m and up to 127 dB re 1 [mu]Pa rms at 1,100 m. Sounds from the 
Caviblaster[supreg] were clearly detectable out to the maximum 
measurement range of 1.1 km. Using the measured transmission loss of 
19.5 log R (Austin 2017), the source level for the Caviblaster[supreg] 
was estimated as 176 dB re 1 [mu]Pa at 1 m. The sounds were broadband 
in nature, concentrated above 500 Hz with a dominant tone near 2 kHz.
    Specifications for the GR 29 Underwater Hydraulic Grinder state 
that the SPL at the operator's position is 97 dB in air (Stanley 2014). 
There are no underwater measurements available for the grinder, so 
using a rough estimate of converting sound level in dB in air to water 
by adding 61.5 dB results in an underwater level of approximately 159 
dB at 1 meter. The measured sound levels for the water jet were used to 
evaluate potential Level A and B acoustic harassment isopleths, but the 
grinder was not included.
    If necessary, Hilcorp may use an underwater pipe cutter to replace 
existing pipeline segments in Cook Inlet. The following tools are 
likely to be used for pipeline cutting activities:
     A diamond wire saw used for remote cutting underwater 
structures such as pipes and I-Beams. These saws use hydraulic power 
delivered by a dedicated power source. The saw usually uses a method 
that pushes the spinning wire through the pipe.
     A hydraulically-powered Guillotine saw which uses an 
orbital cutting movement similar to traditional power saws.
    Generally, sound radiated from the diamond wire cutter is not 
easily discernible from the background noise during the cutting 
operation. The Navy measured underwater sound levels when the diamond 
saw was cutting caissons for replacing piles at an old fuel pier at 
Naval Base Point Loma (Naval Base Point Loma Naval Facilities 
Engineering Command Southwest 2017). They reported an average SPL for a 
single cutter at 136.1-141.4 dB rms at 10 m.
    Specifications for the Guillotine saw state that the SPL at the 
operator's position is 86 dB in air (Wachs 2014). There are no 
underwater measurements available for the grinder, so using a rough 
estimate of converting sound level in dB in air to water by adding 61.5 
dB results in an underwater level of approximately 148 dB at 1 meter. 
Because the measured levels for use of underwater saws do not exceed 
the NMFS criteria, the noise from underwater saws was not considered 
further in this document.
    Scour spans beneath pipelines greater than 23 m (75 ft) have the 
potential to cause pipeline failures. To be conservative, scour spans 
of 15 m (50 ft) or greater identified using multi-beam sonar surveys 
are investigated using dive teams. Divers perform tactile inspections 
to confirm spans greater than 15 m (50 ft). The pipeline is stabilized 
along these spans with Sea-Crete concrete bags. While in the area, the 
divers will also inspect the external coating of the pipeline and take 
cathodic protection readings if corrosion wrap is found to be absent.
    Significant pipeline deficiencies identified during pipeline 
inspections are repaired as soon as practicable using methods 
including, but not limited to, USDOT-approved clamps and/or fiber glass 
wraps, bolt/flange replacements, and manifold replacements. In some 
cases, a water jet may be required to remove sand and gravel from under 
or around the pipeline to allow access for assessment and repair. The 
pipeline surface may also require cleaning using a hydraulic grinder to 
ensure adequate repair. If pipeline replacement is required, an 
underwater pipe cutter such as a diamond wire saw or hydraulically-
powered Guillotine saw may be used. Water jets are the only equipment 
in pipeline stabilization activities that could produce underwater 
noise that have the potential to result in take of marine mammals.
Platform Leg Inspection and Repair
    Hilcorp's platforms in Cook Inlet are inspected on a routine basis. 
Divers and certified rope access technicians visually inspect subsea 
platform legs. These teams also identify and correct significant 
structural deficiencies. Platform leg integrity and pipeline-to-
platform connections beneath the water surface are evaluated by divers 
on a routine basis. Platform legs, braces, and pipeline-to-platform 
connections are evaluated for cathodic protection status, structure 
thickness, excessive marine growth, damage, and scour. If required, 
divers may use a water jet to clean or provide access to the structure. 
If necessary, remedial grinding using a hydraulic underwater grinder 
may be required to determine the extent of damage and/or to prevent 
further crack propagation. All inspection results are recorded and 
significant deficiencies are noted for repair. Elements of subsea 
platform leg inspection and repair that could produce underwater noise 
include: Dive support vessel, hydraulic grinder, water jet.
    Platform leg integrity along the tidal zone is inspected on a 
routine basis. Difficult-to-reach areas may be accessed using either 
commercially-piloted unmanned aerial systems (UAS). Commercially-
piloted UASs may be deployed from the top-side of the platform to 
obtain images of the legs. Generally, the UAS is in the air for 15-20 
minutes at a time due to battery capacity, which allows for two legs 
and part of the underside of the platform to be inspected. The total 
time to inspect a platform is approximately 1.5 hrs of flight time. The 
UAS is operated at a distance of up to 30.5 m (100 ft) from the 
platform at an altitude of 9-15 m (30-50 ft) above sea level. To reduce 
potential harassment of marine mammals, the area around the platform 
will be inspected prior to launch of the UAS to ensure there are no 
flights directly above marine mammals. As no flights will be conducted 
directly over marine mammals, the effects of drone use for routine 
maintenance are not considered further in this application.
Anode Sled Installation and Replacement
    Galvanic and impressed current anode sleds are used to provide 
cathodic protection for the pipelines and platforms in Cook Inlet. 
Galvanic anode sleds do not require a power source and may be installed 
along the length of the pipelines on the seafloor. Impressed current 
anode sleds are located on the seafloor at each of the corners of each 
platform and are powered by rectifiers located on the platform. Anodes 
are placed at the seafloor using dive vessels and hand tools. If 
necessary, a water jet may be used to provide access for proper 
installation. Anodes and/or cables may be stabilized using Sea-Crete 
bags.
Pingers
    Several types of moorings are deployed in support of Hilcorp 
operations; all require an acoustic pinger for location or release. The 
pinger is deployed over the side of a vessel, and a short signal is 
emitted to the mooring device. The mooring device responds with a short 
signal to indicate that the device is working, to indicate range and 
bearing data, or to illicit a release of the unit from the anchor. 
These are used for very short periods of time when needed.
    The types of moorings requiring the use of pingers anticipated to 
be used in the Petition period include acoustic

[[Page 37450]]

moorings during the 3D seismic survey (assumed 2-4 moorings), node 
placement for the 2D survey (used with each node deployment), and 
potential current profilers deployed each season (assumed 2-4 
moorings). The total amount of time per mooring device is less than 10 
minutes during deployment and retrieval. To avoid disturbance, the 
pinger will not be deployed if marine mammals have been observed within 
135 m (443 ft) of the vessel. The short duration of the pinger 
deployment as well as Hilcorp's mitigation suggests take of marine 
mammals from pinger use is unlikely to occur, and pingers are not 
considered further in this analysis.
North Cook Inlet Unit Subsea Well Plugging and Abandonment
    The discovery well in the North Cook Inlet Unit was drilled over 50 
years ago and is planned to be abandoned, so in 2020 Hilcorp Alaska 
plans to conduct a geohazard survey to locate the well and conduct 
plugging and abandonment (P&A) activities for a previously drilled 
subsea exploration well. The geohazard survey location is approximately 
402-804 m (\1/4\-\1/2\ mi) south of the Tyonek platform and will take 
place over approximately seven days with a grid spacing of 
approximately 250 m (820 ft). The suite of equipment used during a 
typical geohazards survey consists of single beam and multi-beam 
echosounders, which provide water depths and seafloor morphology; a 
side scan sonar that provides acoustic images of the seafloor; a sub-
bottom profiler which provides 20 to 200 m (66 to 656 ft) sub-seafloor 
penetration with a 6- to 20-cm (2.4-7.9-in) resolution. The 
echosounders and sub-bottom profilers are generally hull-mounted or 
towed behind a single vessel. The vessel travels at 3-4.5 knots (5.6-
8.3 km/hr).
    After the well has been located, Hilcorp plans to conduct plugging 
and abandonment activities over a 60-90 day time period from May 
through July in 2020. The jack-up rig will be similar to what is 
described above (the Spartan 151 drill rig, or similar). The rig will 
be towed onsite using up to three ocean-going tugs. Once the jack-up 
rig is on location, divers working off a boat will assist in preparing 
the subsea wellhead and mudline hanger for the riser to tie the well to 
the jack-up. At this point, the well will be entered and well casings 
will be plugged with mechanical devices and cement and then cutoff and 
pulled. A shallow cement plug will be set in the surface casing to 3.05 
m (10 ft) below the mudline hanger. The remaining well casings will be 
cutoff and the mudline hanger will be recovered to the deck of the 
jack-up rig for disposal. The well abandonment will be performed in 
accordance to Alaska Oil and Gas Conservation Commission (AOGCC) 
regulations.
Trading Bay Exploratory Drilling
    Hilcorp plans to conduct exploratory drilling activities in the 
Trading Bay area. The specific sites of interest have not yet been 
identified, but the general area is shown in Figure 3 in the 
application. Hilcorp will conduct geohazard surveys over the areas of 
interest to locate potential hazards prior to drilling with the same 
suite of equipment as described above for exploratory drilling in the 
lower Inlet. The survey is expected to take place over 30-60 days in 
2019 from a single vessel.
    The exploratory drilling and well completion activities will take 
place in site-specific areas based on the geohazard survey. Hilcorp 
plans to drill 1-2 exploratory wells in this area in the open water 
season of 2020 with the same equipment and methods as described above 
for lower Inlet exploratory drilling. The noise of routine drilling is 
not considered further as explained in the description of activities in 
the Lower Inlet. However, drive pipe installation and vertical seismic 
profiling will be considered further in the Estimated Take section.
    Required mitigation, monitoring, and reporting measures are 
described in detail later in this document (please see Mitigation and 
Monitoring and Reporting).

Public Comments and Responses

    A notice of NMFS's proposal to issue regulations to Hilcorp was 
published in the Federal Register on April 1, 2019 (84 FR 12330). That 
notice described, in detail, Hilcorp's activity, the marine mammal 
species that may be affected by the activity, and the anticipated 
effects on marine mammals. During the 30-day public comment period, 
NMFS received comments from the Marine Mammal Commission (the 
Commission), several NGOs, the Cook Inlet Regional Citizens Advisory 
Council, and private citizens. These comments and our responses are 
described below.
    Comment 1: The Commission recommended that NMFS ensure all 
applicants include a site-specific stakeholder engagement plan or plan 
of cooperation that includes the required information on the species or 
stocks potentially affected by the proposed activities, a list of 
communities contacted, a summary of input received, a schedule for 
ongoing community engagement, and measures that would be implemented to 
mitigate any potential conflicts with subsistence hunting, as part of 
their LOA requests.
    Response: Hilcorp has shared the stakeholder meeting tracking tool 
with NMFS listing dates, attendees, and discussions specifically on 
marine mammal subsistence hunting. Hilcorp will continue to update NMFS 
and USFWS with this tracking tool. Each annual LOA will include a 
detailed Marine Mammal Mitigation and Monitoring Plan (4MP) for the 
activities to be conducted in that year. The list of communities and 
individuals contacted, date and form of contact, and any issues raised, 
will be posted on the NMFS Incidental Take Program website.
    Comment 2: Several commenters recommended that NMFS defer issuance 
of a final rule to Hilcorpor any other applicant proposing to conduct 
sound-producing activities in Cook Inlet until NMFS has a reasonable 
basis for determining that authorizing any incidental harassment takes 
would not contribute to or exacerbate the decline of Cook Inlet beluga 
whales.
    Response: In accordance with our implementing regulations at 50 CFR 
216.104(c), we use the best available scientific evidence to determine 
whether the taking by the specified activity within the specified 
geographic region will have a negligible impact on the species or stock 
and will not have an unmitigable adverse impact on the availability of 
such species or stock for subsistence uses. Based on the scientific 
evidence available, NMFS determined that the impacts of the oil and gas 
program, which are primarily acoustic in nature, would meet the 
standard of no more than a negligible impact and no unmitigable adverse 
impact on availability of marine mammals for subsistence uses. 
Moreover, Hilcorp proposed and NMFS has required in the rule a rigorous 
mitigation plan to reduce impacts to Cook Inlet beluga whales and other 
marine mammals to the lowest level practicable. Hilcorp is required to 
shutdown airguns if any beluga whale is observed within the Level B 
isopleth (described further in our Ensonified Area section), and 
activities are further restricted by imposing a shutdown of activities 
within a 10 mi (16 km) radius of the Susitna Delta from April 15 
through October 15, which is an important area for beluga feeding and 
calving in the spring and summer months. These shutdown measures are 
more restrictive than the standard shutdown measures typically applied 
and combined with the Susitna Delta exclusion (minimizing adverse 
effects to foraging), they are expected to reduce both the scope and 
severity of potential harassment takes, ensuring that there

[[Page 37451]]

are no energetic impacts from the harassment that would adversely 
affect reproductive rates or survivorship. Additionally, since the 
proposed rule was published, another mitigation area has been added in 
an area and time where belugas have been observed congregating, to 
further minimize impacts. Specifically, no 2D seismic airgun activity 
will be allowed between January 1 and May 31 within the level B 
harassment radius (which may be updated based on the SSV results) of 
the Kasilof River. We are assuming that timing of belugas in the 
Kasilof is likely similar to the timing of belugas in the nearby Kenai 
River (sighings peak in spring and fall, with little to no presence in 
the summer). Belugas may also be present in the Kenai River throughout 
the year; however, there are peaks of beluga presence in spring 
(Castellote et al. 2016; NMFS unpublished data) and sightings also in 
the fall (August through October; NMFS unpublished data). There appears 
to be a steep decline in beluga presence in the Kenai River area during 
the summer (June through August); however, historically belugas were 
seen throughout the summer in the area. Cook Inlet belugas were also 
historically observed in the nearby Kasilof River during aerial surveys 
conducted by ADFG in the late 1970s and early 1980s and NMFS starting 
in 1993 (Shelden et al. 2015b). NMFS' records of opportunistic 
sightings contain thirteen records of beluga sightings in the Kasilof 
River between 1978 and 2015, with half of those sightings occurring 
since 2008 (Shelden et al. 2015b; NMFS unpublished data). In 2018, 
surveys of local residents in the Kenai/Kasilof area were conducted by 
NMFS. There were two reports of sightings of belugas in the Kasilof 
River in April; one of these reports was of a group of around 30 
belugas (NMFS unpublished data).
    Our analysis indicates that issuance of these regulations will not 
contribute to or worsen the observed decline of the Cook Inlet beluga 
whale population. Additionally, the ESA Biological Opinion determined 
that the issuance of this rule is not likely to jeopardize the 
continued existence of the Cook Inlet beluga whales or the western 
distinct population segment of Steller sea lions or to destroy or 
adversely modify Cook Inlet beluga whale critical habitat. The 
Biological Opinion also outlined Terms and Conditions and Reasonable 
and Prudent Measures to reduce impacts, which have been incorporated 
into the rule, including an additional area closure of the Kasilof 
River mouth discussed in the Mitigation section below. Therefore, based 
on the analysis of potential effects, the parameters of the activity, 
and the rigorous mitigation and monitoring program, NMFS determined 
that the activity would have a negligible impact on the Cook Inlet 
beluga whale stock.
    Moreover, the oil and gas activity would take only small numbers of 
marine mammals relative to their population sizes. Further, either 
these takes represent one annual disturbance event for each of these 
individuals, or perhaps a few individuals could be disturbed a few 
times, in which case the number of impacted individual whales is even 
lower. As described in the proposed rule Federal Register notice, NMFS 
used a method that incorporates density of marine mammals overlaid with 
the anticipated ensonified area to calculate an estimated number of 
takes for belugas, which was estimated to be less than 10% of the stock 
abundance, which NMFS considers small.
    Comment 3: Several commenters recommended that NMFS defer issuance 
of Hilcorp's final rule until all activities for which incidental take 
authorizations or regulations have been or are expected to be issued 
are considered with respect to their anticipated, cumulative take of 
Cook Inlet beluga whales, as part of a Programmatic Environmental 
Iimpact Statement under NEPA.
    Response: NMFS originally declared its intent to prepare an 
Environmental Impact Statement (EIS) for oil and gas activities in Cook 
Inlet, Alaska (79 FR 61616; October 14, 2014). However, in a 2017 
Federal Register notice (82 FR 41939; September 5, 2017), NMFS 
indicated that due to a reduced number of Incidental Take Authorization 
(ITA) requests in the region, combined with funding constraints at that 
time, we were postponing any potential preparation of an EIS for oil 
and gas activities in Cook Inlet. As stated in the 2017 Federal 
Register notice, should the number of ITA requests, or anticipated 
requests, noticeably increase, NMFS will re-evaluate whether 
preparation of an EIS is necessary. Currently, the number of ITA 
requests for activities that may affect marine mammals in Cook Inlet is 
at such a level that preparation of an EIS is not yet necessary. 
Nonetheless, under NEPA, NMFS is required to consider cumulative 
effects of other potential activities in the same geographic area, and 
these are discussed in greater detail in the Final Environmental 
Assessment (EA).
    Comment 4: The Commission also recommended that NMFS establish 
annual limits on the total number and type of takes that are authorized 
for all sound-producing activities in Cook Inlet before issuing the 
final rule.
    Response: As mentioned above, NMFS is required to make its required 
determinations at the specified activities level (i.e., the entire 
project described in the application) under the MMPA. Setting limits on 
the number and types of takes across individual activity pieces is not 
necessary, as there are no takes associated with any specific portion 
of the project that have differential or more severe impacts such that 
they require individual management or limits. Further, there are few 
incidental takes of Cook Inlet beluga whales currently authorized in 
Cook Inlet, and the projects for which takes are authorized are 
separated spatially and temporally. NMFS explores the effects of 
potential overlap in projects and the effects of sound sources other 
than sound sources resulting in incidental take on Cook Inlet beluga 
whales in the Cumulative Effects section of the Final EA.
    Comment 5: The Commission recommended that NMFS address and fix 
inconsistencies with respect to information provided regarding the 
referenced sound sources.
    Response: NMFS clarified which sound sources were referenced to 1 
m. NMFS also clarified that it does not expect that the sounds produced 
by hydraulic grinders or pipe cutters are likely to result in take. 
Therefore, NMFS did not analyze those source any further.
    Comment 6: The Commission recommended that NMFS require Hilcorp to 
ensure that the total number of days for each activity is accurate and 
consistent, and recommended that NMFS revise the number of days used to 
estimate the number of marine mammal takes for each of the proposed 
activities based on the number of days each type of activity is 
scheduled to occur regardless of the duration of those activities on a 
given day.
    Response: The number of days of activity have been updated in the 
calculations for take estimates, and an updated Table 1 is included in 
the project description above.
    Comment 7: The Commission recommended that NMFS require Hilcorp to 
revise the geohazard survey durations for each of the well sites (the 
four lower Cook Inlet OCS sites, the North Cook Inlet Unit site, and 
the two Trading Bay area sites) and re-estimate the number of marine 
mammal takes.
    Response: Geohazard duration was calculated based on a worst-case 
scenario, as the precise scope of work will depend on results of other 
surveys. Therefore, the original estimate is still appropriate: 2,400 m 
of monitoring

[[Page 37452]]

distance in both directions yields 4,800 m total length of transect. 
This 4,800 m of transect distance, divided by 150 m transect width 
yields 32 transects. 4,800 m transect length multiplied by 32 transects 
yields 153.6 km transect length to be surveyed. If the distance is 
covered at a speed of 7.41 km/hour this results in 0.65 hours (38 
minutes) to survey each transect. If surveying can occur for 12 hours 
per day, this results in 7.77 days to survey one well grid. This 
duration (7/77 days) multiplied by the number of wells results in 
durations of: 31 days for OCS wells, eight days for Northern Cook Inlet 
wells, and 15.5 days for Trading Bay wells.
    Comment 8: The Commission recommended that NMFS determine which of 
the proposed activities will actually occur this year and which will be 
delayed until 2020, and revise the numbers of marine mammal takes 
accordingly.
    Response: As noted above, these activities are progressive and 
dependent on results from the previous year, so predicting activities 
by year is challenging. Hilcorp has provided a ``worst case'' 5-year 
scenario of activities. Based on the predicted schedule, we have used 
June 1 to May 31 as the annual scenario described in the Estimated Take 
Section below. Therefore, we attempt to use ``Year 1 or Season 1'' 
terminology, as these activities are not confined to single calendar 
years (January to December).
    One of the primary challenges with the forecasting annual 
activities is how to break up and analyze components associated with 
the OCS exploratory drilling (i.e., VSP, conductor pipe driving, 
geohazard). Hilcorp has clarified that the plan is to drill all 4 wells 
between June 1 2020-2021 (Year 2), as long as everything goes well. So, 
we have included a shallow hazard survey in April-May 2020 (Year 1) 
over 2 of the 4 wells, and then a suite of drilling activities (VSP, 
conductor pipe driving) over all 4 wells in June 2020-2021 (Year 2), 
with the other 2 wells surveyed for shallow hazards (shallow hazard 
survey must be conducted within a few months of the planned drilling, 
so we would do shallow hazard in between the wells). To be 
conservative, we have included drilling activities (VSP, conductor 
pipe, and shallow hazard) for 1 of 4 wells in Years 3 and 4, in the 
event OCS activities take longer than the planned 1 year. Tables 11 
through 18 have been updated accordingly.
    Comment 9: The Commission noted several inconsistencies regarding 
source levels presented in either the application or the proposed rule 
which did not result in the correct outputs for Level A harassment 
isopleths. The Commission did not agree with several pulse durations 
used in the proposed rule, including the chosen pulse duration for the 
profiler (boomer), which the Commission suggests is too long at 90 msec 
for a repetition rate of 30 msec, as well as VSP and impact pile 
driving, for which the Commission suggests the pulse durations were too 
short at 20 msec. The Commission recommended that NMFS recalculate all 
of the Level A harassment zones and revise the numbers of marine mammal 
takes and mitigation measures accordingly.
    Response: The exposure estimates have been updated using the NMFS 
2018 guidance and updated user spreadsheet inputs. Per the Commission's 
comments, the boomer pulse duration was adjusted to 0.1 sec (100 ms). 
The VSP pulse duration was kept at 0.02 sec (20 ms). When speaking to 
the Hilcorp engineers, they indicated that the seismic pulse for VSP is 
generally the same as for 3D seismic survey, or generally 20 ms . The 
impact pipe driving was adjusted to 0.1 sec (100 ms) per the 
Commission's comments. It is important to note that the specific 
equipment for everything other than the 3D seismic survey is not known 
at this time because contractors have not been selected; these are 
estimates only, although the equipment will be required to be within 
the parameters outlined in the proposed rule. If peak measurements were 
not available, the RMS was used to calculate peak. Many of the SSV 
reports prior to 2016 did not include peak or SEL. They only included 
RMS for the 190/180/160/120 dB thresholds, such as the VSP and water 
jet.
    The inputs used are as follows:
    3D/2D seismic survey: 217 dB peak/185 dB SEL @100 m; 2.05 m/s 
vessel speed, pulse duration 0.02 s, repetition rate every 6 s;
     Profiler (boomer): 212 dB peak @1 m; 2.05 m/s vessel 
speed, pulse duration 0.1 s, repetition rate every 6 s;
     VSP: 227 dB rms @1 m; 4 hrs per day; pulse duration 0.02 
s; repetition rate 6 s;
     Water jet: 176 dB rms @1 m; 3 hrs per day;
     Pipe driving: 195 dB rms @55 m; 1 pile per day; 0.100 s; 
25 strikes per pile
     Vib pile driving: 160 dB rms @10 m; 5 piles per day; 90 
min per pile
    Table 4 has been updated accordingly.
    Comment 10: The Commission recommended that, until the behavior 
thresholds are updated, NMFS require Hilcorp to use the 120- dB re 1 
[mu]Pa threshold rather than the 160-dB re 1 [mu]Pa threshold for 
intermittent, non-impulsive sources, such as chirps.
    Response: Please see our Notice of Proposed Rulemaking (83 FR 
37638; August 1, 2018) for the discussion related to acoustic 
terminology and thresholds. The Commission repeats a recommendation 
made in prior letters concerning proposed authorization of take 
incidental to the use of scientific sonars (such as echosounders). As 
we have described in responses to those prior comments (e.g., 83 FR 
36370), our evaluation of the available information leads us to 
disagree with this recommendation. After review of the Commission's 
recommendation in this case, our assessment is unchanged. While the 
Commission presents certain valid points in attempting to justify their 
recommendation (e.g., certain sensitive species are known to respond to 
sound exposures at lower levels), these points do not ultimately 
support the recommendation.
    First, we provide here some necessary background on implementation 
of acoustic thresholds. NMFS has historically used generalized acoustic 
thresholds based on received levels to predict the occurrence of 
behavioral disturbance rising to the level of Level B harassment, given 
the practical need to use a relatively simple threshold based on 
information that is available for most activities. Thresholds were 
selected largely in consideration of measured avoidance responses of 
mysticete whales to airgun signals and to industrial noise sources, 
such as drilling. The selected thresholds of 160 dB rms SPL and 120 dB 
rms SPL, respectively, have been extended for use for estimation of 
behavioral disturbance rising to the level of Level B harassment 
associated with noise exposure from sources associated with other 
common activities.
    The Commission misinterpreted how NMFS characterizes scientific 
sonars, so we provide clarification here. Sound sources can be divided 
into broad categories based on various criteria or for various 
purposes. As discussed by Richardson et al. (1995), source 
characteristics include strength of signal amplitude, distribution of 
sound frequency and, importantly in context of these thresholds, 
variability over time. With regard to temporal properties, sounds are 
generally considered to be either continuous or transient (i.e., 
intermittent). Continuous sounds, which are produced by the industrial 
noise sources for which the 120-dB behavioral threshold was selected, 
are simply those for which sound pressure level remain above ambient 
sound during the observation period (ANSI,

[[Page 37453]]

2005). Intermittent sounds are defined as sounds with interrupted 
levels of low or no sound (NIOSH, 1998). Simply put, a continuous noise 
source produces a signal that continues over time, while an 
intermittent source produces signals of relatively short duration 
having an obvious start and end with predictable patterns of bursts of 
sound and silent periods (i.e., duty cycle) (Richardson and Malme, 
1993). It is this fundamental temporal distinction that is most 
important for categorizing sound types in terms of their potential to 
cause a behavioral response. For example, Gomez et al. (2016) found a 
significant relationship between source type and marine mammal 
behavioral response when sources were split into continuous (e.g., 
shipping, icebreaking, drilling) versus intermittent (e.g., sonar, 
seismic, explosives) types. In addition, there have been various 
studies noting differences in responses to intermittent and continuous 
sound sources for other species (e.g., Neo et al., 2014; Radford et 
al., 2016; Nichols et al., 2015).
    Sound sources may also be categorized based on their potential to 
cause physical damage to auditory structures and/or result in threshold 
shifts. In contrast to the temporal distinction discussed above, the 
most important factor for understanding the differing potential for 
these outcomes across source types is simply whether the sound is 
impulsive or not. Impulsive sounds, such as those produced by airguns, 
are defined as sounds which are typically transient, brief (< 1 sec), 
broadband, and which consist of a high peak pressure with rapid rise 
time and rapid decay (ANSI, 1986; NIOSH, 1998). These sounds are 
generally considered to have greater potential to cause auditory injury 
and/or result in threshold shifts. Non-impulsive sounds can be 
broadband or narrowband (i.e., tonal), brief or prolonged, and 
continuous or intermittent, and typically do not have the high peak 
pressure with rapid rise/decay time that impulsive sounds have (ANSI, 
1995; NIOSH, 1998). Because the selection of the 160-dB behavioral 
threshold was focused largely on airgun signals, this threshold has 
historically been referred to as the ``impulse noise'' threshold 
(including by NMFS). However, this longstanding confusion in 
terminology--i.e., the erroneous impulsive/continuous dichotomy--
presents a narrow view of the sound sources to which the thresholds 
apply and inappropriately implies a limitation in scope of 
applicability for the 160-dB behavioral threshold in particular.
    An impulsive sound is by definition intermittent; however, not all 
intermittent sounds are impulsive. Many sound sources for which it is 
generally appropriate to consider the authorization of incidental take 
are in fact either impulsive (and intermittent) (e.g., impact pile 
driving) or continuous (and non-impulsive) (e.g., vibratory pile 
driving). However, scientific sonars present a less common case where 
the sound produced is considered intermittent but non-impulsive. Herein 
lies the crux of the Commission's argument, i.e., that because chirps 
used by Hilcorp are not impulsive sound sources, they must be assessed 
using the 120-dB behavioral threshold appropriate for continuous noise 
sources. However, given the existing paradigm--dichotomous thresholds 
appropriate for generic use in evaluating the potential for behavioral 
disturbance rising to the level of Level B harassment resulting from 
exposure to continuous or intermittent sound sources--the Commission 
does not adequately explain why potential harassment from an 
intermittent sound source should be evaluated using a threshold 
developed for use with continuous sound sources. As we have stated in 
prior responses to this recommendation, consideration of the preceding 
factors leads to a conclusion that the 160-dB threshold is more 
appropriate for use than the 120-dB threshold.
    As noted above, the Commission first claims generically that we are 
using an incorrect threshold, because scientific sonars do not produce 
impulse noise. However, in bridging the gap from this generic assertion 
to their specific recommendation that the 120-dB continuous noise 
threshold should be used, the Commission makes several leaps of logic 
that we address here. The Commission's justification is in large part 
seemingly based on the Commission's citation to examples in the 
literature of the most sensitive species responding at lower received 
levels to sources dissimilar to those considered here. There are three 
critical errors in this approach.
    First, the citation of examples of animals ``responding to sound'' 
does not equate to Level B harassment, as defined by the MMPA. As noted 
above under ``Background,'' the MMPA defines Level B harassment as acts 
with the potential to disturb a marine mammal by causing disruption of 
behavioral patterns. While it is possible that some animals do in fact 
experience Level B harassment upon exposure to intermittent sounds at 
received levels less than the 160-dB threshold, this is not in and of 
itself adequate justification for using a lower threshold. Implicit in 
the use of a step function for quantifying Level B harassment is the 
realistic assumption, due to behavioral context and other factors, that 
some animals exposed to received levels below the threshold will in 
fact experience harassment, while others exposed to levels above the 
threshold will not. Moreover, a brief, transient behavioral response 
alone should not necessarily be considered as having the potential to 
disturb by disrupting behavioral patterns.
    We note that the Commission cites Lurton and DeRuiter (2011), which 
suggests 130 dB as a reasonable behavioral response threshold. Given 
that a ``behavioral response threshold'' does not equate to a Level B 
harassment threshold, we are unsure about the potential implications. 
In addition, Lurton and DeRuiter casually offered this threshold as a 
result of a ``conservative approach'' using ``response thresholds of 
the most sensitive species studied to date.'' NMFS does not agree with 
any suggestion that this equates to an appropriate Level B harassment 
threshold. Watkins and Schevill (1975) noted that when sperm whales 
were exposed to ``temporarily interrupted'' sound production in 
response to sound from pingers, no avoidance behavior was observed, and 
the authors note that ``there appeared to be no startle reactions, no 
sudden movements, or changes in the activity of the whales.'' Kastelein 
et al. (2006a) described the response of harbor porpoise to an 
experimental acoustic alarm (discussed below; averaged source level of 
145 dB), while also noting that a striped dolphin showed no reaction to 
the alarm, despite both species being able to clearly detect the 
signal.
    Second, unlike the studies discussed above, which relate to 
echosounders, many of the cited studies do not present a relevant 
comparison. These studies discuss sources that are not appropriately or 
easily compared to the sources considered here, and address responses 
of animals in experimental environments that are not appropriately 
compared to the likely exposure context here. For example, aside from 
the well-developed literature concerning ``acoustic harassment'' or 
``acoustic deterrent'' devices--which are obviously designed for the 
express purpose of harassing marine mammals (usually specific species 
or groups)--Kastelein et al. (2006b) describe harbor seal responses to 
signals used as part of an underwater data communication network. In 
this case, seals in a pool were exposed to signals of relatively long 
duration (1-2 seconds) and high duty cycle for 15 minutes, with 
experimental signals of continuously

[[Page 37454]]

varying frequency, three different sound blocks, or frequency sweeps. 
These seals swam away from the sound (though they did not attempt to 
reduce exposure by putting their heads out of the water), but this 
result is of questionable relevance to understanding the likely 
response of seals in the wild that may be exposed to a 1-ms single-
frequency signal from an echosounder moving past the seal as a 
transient stimulus.
    Some studies do not provide a relevant comparison not only because 
of differences in the source, but because they address sources (in some 
cases multiple sources) that are stationary (for extended periods of 
time in some cases); whereas, Hilcorp's use of sub-bottom profilers 
will be infrequent and transient in any given location. Morton (2000) 
presents only brief speculation that an observed decline in abundance 
of Pacific white-sided dolphin coincided with introduction of 194-dB 
(source level) acoustic deterrent devices--an observation that is not 
relevant to consideration of a single mobile source that would be 
transient in space and time relevant to a receiver. Morton and Symonds 
(2002) similarly address displacement from a specific area due to a 
profusion of ``high-powered'' deterrent devices (the same 194-dB system 
discussed briefly in Morton (2000)) placed in restricted passages for 
extended time periods (6 years).
    Third, the Commission's sources tend to pertain to the most 
sensitive species, which does not support an argument that the 120-dB 
threshold should be applied to all species. NMFS has acknowledged that 
the scientific evidence indicates that certain species are, in general, 
more acoustically sensitive than others. In particular, harbor porpoise 
and beaked whales are considered to be behaviorally sensitive, and it 
may be appropriate to consider use of lower Level B harassment 
thresholds for these species. NMFS is considering this issue in its 
current work of developing new guidelines for assessing Level B 
harassment; however, until this work is completed and new guidelines 
are identified (if appropriate), the existing generic thresholds are 
retained. Moreover, as is discussed above for other reasons, the 
majority of examples cited by the Commission are of limited relevance 
in terms of comparison of sound sources. In support of their statement 
that numerous researchers have observed marine mammals responding to 
sound from sources claimed to be similar to those considered herein, 
the Commission cites numerous studies; however, the vast majority of 
these studies address responses of harbor porpoise or beaked whales to 
various types of acoustic alarms or deterrent devices.
    We acknowledge that the Commission presents legitimate points in 
support of defining a threshold specific to non-impulsive, intermittent 
sources, and that, among the large number of cited studies, there are a 
few that show relevant results of individual animals responding to 
exposure at lower received levels in ways that could be considered 
harassment under the MMPA. As noted in a previous comment response, 
NMFS is currently engaged in an ongoing effort to develop updated 
guidance regarding the effects of anthropogenic sound on marine mammal 
behavior. However, prior to conclusion of this effort, NMFS will 
continue using the historical Level B harassment thresholds (or 
derivations thereof) and will appropriately evaluate behavioral 
disturbance rising to the level of Level B harassment due to 
intermittent sound sources relative to the 160-dB threshold.
    Comment 11: The Commission recommended that NMFS clarify what 
density estimates were used to determine the numbers of takes and 
ensure the density estimates for marine mammals other than beluga 
whales are consistent with its stated method for calculating densities 
based on sightings from aerial surveys from 2000-2016.
    Response: The densities used are detailed in Table 7 for Cook Inlet 
beluga whales and Table 8 for all other marine mammal species. Table 8 
in the proposed rule included incorrect density estimates from a 
previous version of exposure calculations that included hours surveyed 
as part of the calculation, while also correcting for distance. The 
densities in Table 9 of this final rule are the correct densities based 
on NMFS aerial survey data, using number of animals sighted divided by 
distance surveyed. The values in Table 9 are the densities used to 
calculate exposure estimates for this final rule.
    Comment 12: The Commission recommended that NMFS specify the 
relevant densities, ensonified areas associated with both Level A and B 
harassment for the various proposed activities, the number of days each 
activity would occur, and finally the numbers of takes prior to issuing 
the final rule.
    Response: Based on updated durations of activities, ensonified 
areas and updated exposure estimates are contained in the relevant 
tables throughout the final rule.
    Comment 13: The Commission recommended that NMFS provide the 
numbers of beluga whales that could be taken during the proposed 
activities and any assumptions made to reduce those takes.
    Response: The method for estimating takes of Cook Inlet beluga 
whale is described in the Take Estimation section below. The number of 
beluga whales that could be exposed during each year is listed in 
Tables 12-16. There are no assumptions made to reduce authorized take 
from estimated exposure.
    Comment 14: The Commission recommended that NMFS authorize the 
total estimated number of harbor seal takes in a given year for each 
year from 2019-2024 rather than presuming only 25 percent of the 
population would be taken during the course of the five years of 
activities.
    Response: NMFS is authorizing the total number of instances of 
exposure resulting from the take calculation. Note that NMFS is not 
equating the total number of instances of exposure to the number of 
individual harbor seals that may be taken, as that would lead to an 
overestimation of harbor seal occurrence in the survey area. The 
explanation for why the calculation results in overestimation of 
individuals is described in the Take Estimation section below. Based on 
consideration of the factors described further in the Estimated Take 
section, the number of individual harbor seals that may be taken by 
Level A or Level B harassment will not exceed 25 percent of the 
population. However, NMFS agrees with this comment from the Commission, 
and is authorizing an annual number of harbor seal takes rather than a 
certain number over the five years of activities authorized by this 
rule.
    Comment 15: The Commission recommended that, in the final rule, 
NMFS explicitly require Hilcorp to conduct SSVs at the beginning of the 
proposed activities for 3D seismic and sub-bottom profiler surveys and 
use those measurements to verify and adjust, if necessary, the extents 
of the Level A and B harassment zones.
    Response: SSVs for 3D seismic and sub-bottom profiler use are 
required in the final rule.
    Comment 16: The Commission recommended that NMFS (1) specify how 
Hilcorp should enumerate the numbers of animals taken when observers 
are only monitoring a portion of the Level B harassment zones, and (2) 
require Hilcorp to keep a tally of the numbers of marine mammals taken, 
alert NMFS when the number of authorized beluga whale takes has been 
reached, and follow any guidance provided.

[[Page 37455]]

    Response: A description of how Hilcorp should record and report 
takes has been added to the Monitoring section below. The specific 
extrapolation method to be used by Hilcorp will be submitted to NMFS 
Alaska Regional Office (AKR) and the Office of Protected Resources 
(OPR) for approval before seismic activity may begin. Hilcorp will 
contact NMFS AKR and OPR when the number of takes authorized for that 
year has been reached.
    Comment 17: The Commission recommends that NMFS prohibit Hilcorp 
from using power-down procedures as a mitigation measure for seismic 
surveys in Cook Inlet. The Center for Biological Diversity (CBD) 
commented that power-downs should be required for all species within 
the safety zone.
    Response: As noted by the Commission, a power down requirement 
would potentially lead to the need for termination of survey lines. The 
need to revisit missed survey lines to reacquire data is likely to 
result in an overall increase in the total sound energy input to the 
marine environment and an increase in the total duration over which the 
survey is active in a given area. NMFS has removed the use of power 
downs as a mitigation measure for seismic surveys in this rulemaking.
    Comment 18: The Commission recommends that NMFS prohibit the use of 
a mitigation gun to avoid implementing ramp-up procedures.
    Response: Mitigation guns have been removed as a mitigation measure 
from the final rule. While it is possible that use of a mitigation gun 
could provide a ``warning'' sound to marine mammals in the vicinity of 
the seismic survey source, it is likely that the use of mitigation guns 
would emit sound into the water at a time that the environment would 
otherwise be devoid of any airgun-related sound.
    Comment 19: The Commission recommends that NMFS specify in the 
final rule that observers be placed on the source vessel (for seismic 
and geohazard surveys) or on the drilling rig (for pile/pipe driving 
and VSP) to monitor the Level A and B harassment zones for the proposed 
sound-generating activities.
    Response: NMFS has specified placement of at least two on-duty PSOs 
on the source vessel (for seismic and geohazard surveys) or one PSO on 
the drill rig (for pipe driving and VSP). However, for seismic 
surveying, at least one on-duty PSO will be required to be stationed on 
a mitigation vessel.
    Comment 20: The Commission recommended that NMFS (1) consult with 
Hilcorp regarding the numerous issues raised in this letter and direct 
the applicant to revise the application accordingly, and (2) publish a 
revised proposed rule prior to issuance of a final rule.
    Response: NMFS has consulted with Hilcorp, which has corrected 
errors contained in their Petition for regulations, and in this final 
rule NMFS has corrected errors that were in the proposed rule. These 
corrections are discussed in this final rule in the Estimated Take 
sections. As these corrections did not substantively change NMFS' 
findings, a revised proposed rule was not published.
    Comment 21: The International Association of Geophysical 
Contractors (IAGC) commented that a 7,300 m shutdown zone for beluga 
whales was unnecessary and impractical.
    Response: NMFS has revised the mitigation and monitoring scheme, 
taking into consideration comments received during the public comment 
period. A 7,300 m monitoring zone is not required as it is not feasible 
or practicable to cover that area during seismic surveying. Instead, a 
1,500 m safety zone will be implemented. This 1,500 m safety zone 
requires observers on the source vessel and the mitigation vessel to 
observe to a distance of 1,500 m during seismic activity. Hilcorp plans 
to conduct a SSV for 3D seismic surveys during the course of the 
activities authorized by this rule, and mitigation and monitoring may 
be adjusted based on the results of the SSV. However, in light of 
concerns surrounding the status of Cook Inlet beluga whales, NMFS 
implemented a shutdown measure that requires Hilcorp to shut down 
active sound sources from which take could occur if a Cook Inlet beluga 
whale is sighted at any distance within the relevant Level B harassment 
isopleths.
    Comment 22: The IAGC commented that the specifications for data 
collected by protected species observers were impractical, and that 
collecting data on environmental variables distracted observers from 
monitoring safety and exclusion zones.
    Response: NMFS disagrees with the commenter about the burden of 
collecting the required information. Applicants are required to collect 
information that improves our understanding of the effects of their 
activity. While an applicant could propose that a separate team or 
project could accomplish those objectives, Hilcorp proposed that their 
own PSOs collect the required monitoring information simultaneously 
with their observation duties. Information about environmental 
conditions informs detectability of certain species and provides detail 
about potential accuracy of the reported information. The IAGC also 
commented that recording these details could be distracting for a PSO. 
However, for many activities, more than one PSO is on watch 
simultaneously to ensure monitoring coverage is not compromised while 
recording other essential pieces of information.
    Comment 23: The IAGC commented that sound source verification 
studies are complicated and burdensome for operators, as the results 
are highly variable and should be removed from the final rule 
requirements.
    Response: NMFS disagrees with the IAGC comments that the 
requirement for SSVs should be removed. Cook Inlet is a unique 
environment with characteristics that are difficult to quantify using 
generic sound source studies. Additionally, very few SSVs of sub-bottom 
profiler sounds are available to characterize potential disturbance 
from the use of a sub-bottom profiler, which is an increasingly used 
technology. While SSVs can be unusable if conducted improperly, Hilcorp 
has agreed to submit their SSV plans to NMFS' acousticians to ensure 
that the data will be collected in a format that is useful in the 
future. Additionally, mitigation and monitoring measures tied to 
acoustic zones may be adjusted based on the results of the SSV.
    Comment 24: The Environmental Investigation Agency (EIA) commented 
that NMFS did not consider all possible sources of take by discounting 
take of marine mammals from echosounders and side scan sonar operating 
at frequencies greater than 220 kHz but producing subharmonics within 
hearing ranges of marine mammals.
    Response: The intended operating frequencies of this equipment is 
at 200kHz or greater, which is outside the hearing range of marine 
mammals in Cook Inlet. Subharmonics produced in the 90-130kHz range are 
not an intended byproduct of the equipment, and when the equipment is 
set up correctly, subharmonics should not be produced. As stated in the 
Deng et al. (2015) study cited by the EIA, the subharmonics produced 
were at sound levels so low that they were ``well below potentially 
harmful levels''.
    Comment 25: The EIA commented that NMFS failed to reflect the full 
potential impact of noise sources, specifically the sensitivity of Cook 
Inlet beluga whales to anthropogenic noise.
    Response: NMFS has considered the sensitivity of all marine mammal 
species in Cook Inlet to anthropogenic activity, including the 
sensitivity of Cook Inlet beluga whales. Literature

[[Page 37456]]

indicating the responses of beluga whales to anthropogenic activity, 
particularly seismic activity in the Beaufort Sea, is considered in 
this final rule. Behavioral responses to pile driving have also been 
considered in the rule, as NMFS discussed avoidance behavior as a 
possible effect of Hilcorp's activity. The short term nature of the 
activity in any one location, either through the use of mobile sources 
or localized drill activity that continues for a short amount of time 
before moving to a different drill rig, allows beluga whales to return 
to favored areas while activity continues in other locations. 
Additionally, the area identified as most sensitive for Cook Inlet 
beluga whales, the area of the Susitna Delta between the Susitna and 
Beluga Rivers, has been excluded from activity during periods when 
beluga whales are known to occur frequently. While literature suggests 
that beluga whales may react to anthropogenic sounds, by requesting 
take Hilcorp is requesting permission to incidentally harass marine 
mammals by emitting anthropogenic noise. Migitation and monitoring 
measures required by NMFS are directed at reducing potential impact of 
the sound, not to completely avoid behavioral harassment.
    Comment 26: The EIA commented that NMFS did not conduct an adequate 
assessment of cumulative effects in the draft Environmental Assessment 
(EA).
    Response: NMFS fulfilled its requirement under NEPA to analyze 
potential effects of Hilcorp's activities in conjunction with other 
activities that may overlap spatially or temporally in the past, 
present, or reasonably foreseeable future, with Hilcorp's activities or 
the marine mammals that may be impacted by these activities. During 
public comment, additional activities that should be included in the 
cumulative impacts assessment were raised, and these activities have 
been included in the final Environmental Assessment.
    Comment 27: The EIA expressed concern about potential renewal of 
the proposed incidental take authorization.
    Response: NMFS does not propose to renew the incidental take 
regulations in this final rule. The regulations would be valid for five 
years from the date of issuance with a maximum of five annual Letters 
of Authorization requested under these regulations.
    Comment 28: The Cook Inlet Regional Citizens Advisory Council 
(CIRCAC) commented that the dates proposed for 3D seismic activity in 
the proposed rule differ from the dates set forth in Hilcorp's Marine 
Mammal Mitigation and Monitoring Plan.
    Response: During the time period encompassing the process of 
requesting incidental take regulations, drafting the proposed rule, and 
preparing this final rule, Hilcorp's proposed timelines have been 
delayed slightly from what was intended in their original application. 
To account for these delays, tables in this final rule referring to 
amounts of take authorized by year have been labeled using Year 1, Year 
2, etc., instead of using specific calendar dates.
    Comment 29: The CIRCAC expressed concern regarding the scope of the 
activities covered under the rulemaking and the ambiguity in dates and 
locations of certain components of the activities.
    Response: While there is potential uncertainty associated with 
these activities, NFMS required and Hilcorp provided information on 
specified activities, as well as a specified geographic area. Hilcorp 
provided details about all potential activities as well as where and 
when they could occur. Hilcorp's application included information on 
the maximum possible level of activity; therefore, any changes to these 
planned activities in the future would result in fewer activities being 
carried out than initially proposed. If for example, geohazard surveys 
do not indicate that it is feasible to conduct exploratory drilling 
activities at a particular site, Hilcorp would be conducting less 
activity than considered in this rule, and the effects would be less, 
not more, impactful to marine mammals than those effects analyzed in 
this rule. Additionally, to ensure the activities are within the scope 
of this rule, NMFS is requiring Hilcorp to obtain annual Letters of 
Authorization, thereby requiring Hilcorp to provide specific detail 
about each year's activities so that NMFS can determine whether these 
activities comport with the regulations.
    Comment 30: The CIRCAC commented on a lack of description of 
effects from developing the causeway inside Chinitna Bay on Cook Inlet 
beluga whales and their prey species. They also commented that proposed 
pile driving activities in Chinitna Bay overlap with time periods when 
beluga whales have been documented in the Chinitna Bay.
    Response: NMFS analyzed the effects of potential pile driving on 
marine mammal species for the building of the causeway at Chinitna Bay. 
Potential erosion of the area due to the creation of the causeway is 
not likely to result in take of marine mammals, and therefore is not 
part of this incidental take authorization. As referenced in the 
comment letter, erosion of habitat for prey species, such as crangonid 
shrimp and polychaetes, could certainly be a possible impact resulting 
from the causeway construction. However, the size of the causeway and 
its construction area, relative to the total available habitat for 
crangonid shrimp or polychaetes in middle and lower Cook Inlet, is 
likely very small. The construction in this area will include pile 
driving and rock laying for construction of a causeway extending 1,200 
ft into the bay. The Iniskin causeway will result in 2.65 acres of 
seafloor disturbance and temporary loss of habitat. The causeway itself 
is likely to impact local streams and the anadromous fish (including 
smolt) by altering the flow of water within Chinitna Bay. The turbidity 
resulting from pile driving and rock laying is expected to be localized 
and largely indistinguishable from ambient turbidity. After the 
causeway is no longer needed for the project, it is proposed that rock 
fill be removed and relocated to a landowner- approved upland fill 
area, exposing the natural mud flat surface. Tidal action, wave action, 
and currents will naturally restore the area disturbed by the causeway. 
Overall, seafloor disturbance and habitat alteration could have highly 
localized, short-term effects on marine mammals and their prey species. 
Potential effects from seafloor disturbance are likely to limit the 
foraging quality of the disturbed area temporarily, but prey species 
would likely navigate to suitable nearby habitat until the habitat was 
returned to acceptable conditions for these species. Accordingly, 
marine mammals would likely forage elsewhere, and any effects on their 
foraging would be immeasurably small, and thus insignificant.
    Comment 31: Several commenters suggested that passive acoustic 
monitoring (PAM) should be used in addition to the proposed mitigation 
and monitoring. They highlight environmental differences between upper 
and lower Cook Inlet and suggest PAM would be successful in the lower 
Inlet.
    Response: NMFS has required PAM in several previous incidental take 
authorizations in Cook Inlet, including activity in mid and lower Cook 
Inlet. These efforts have not resulted in successful deployment of PAM 
or useful detections of marine mammals to inform mitigation and 
monitoring during the activities. NMFS looks forward to advances in 
technology that could make PAM a practicable mitigation measure in 
these areas in the future. However, at the time of this rulemaking, 
NMFS has elected to require additional mitigation

[[Page 37457]]

measures outside of PAM to mediate impacts of Hilcorp's activities on 
marine mammals, including the use of aerial surveys for spotting beluga 
whales in the area and the use of additional mitigation vessels to 
expand visual PSO coverage.
    Comment 32: The CIRCAC commented that there are no monitoring 
requirements related to marine mammal prey species.
    Response: The monitoring requirement under MMPA Section 
101(a)(5)(A) is intended to provide information that helps us 
understand the impacts of the specified activity on the affected 
species and stocks. While monitoring of prey species could be included 
as part of a monitoring plan, if the applicant submitted it, it is not 
required, and Hilcorp did not propose it. Hilcorp will conduct visual 
observations of marine mammals before, during and after sound-producing 
activities that have the potential to result in take. These visual 
observations will help us better understand the impacts of activities 
on behavioral responses of marine mammals to particular types of sound. 
These monitoring efforts can provide valuable information on species 
occurrence and seasonality of occurance, more detail regarding habitat 
use, and information about temporary habitat abandonment and timing of 
animal return to the affected area.
    Comment 33: The Center for Biological Diversity (CBD) commented 
that NMFS did not consider population-level effects of noise from the 
proposed activities.
    Response: NMFS has carefully reviewed the best available scientific 
information in assessing impacts to marine mammals and recognizes that 
these activities have the potential to impact marine mammals through 
threshold shifts, behavioral effects, stress responses, and auditory 
masking. However, NMFS has determined that the nature of such 
potentially transitory exposure--any given location will be exposed to 
noise from these activities only relatively briefly and infrequently--
means that the likelihood of any impacts to fitness from the authorized 
take, including from detrimental energetic effects or reproductive 
impacts, is low. NMFS has also prescribed a robust suite of mitigation 
measures, such as a beluga-specific exclusion zone and extended 
distance shutdown zone, that are expected to further reduce the 
duration and intensity of acoustic exposure, while limiting the 
potential severity of any possible behavioral disruption. Further 
characterization of these short-term, recoverable effects with respect 
to long-term population success are unknown. However, disruption to 
behaviors such as feeding, breeding, and vocalizing, which are 
essential functions, are analyzed within this rule.
    Comment 34: The CBD commented that NMFS underestimated take of Cook 
Inlet beluga whales by not accounting for beluga hearing sensitivities 
and using densities based on seasonal aerial surveys.
    Response: NMFS' take estimate for Cook Inlet belugas uses the best 
available science concerning hearing sensitivities, occurrence, and 
seasonality of the species. Regarding hearing sensitivity, the NMFS 
Acoustic Guidance uses the best available science, vetted through peer 
review, to characterize the thresholds for onset of TTS and PTS in 
marine mammal hearing for all underwater sounds. To best assess these 
onset thresholds for all marine mammals, the species were divided into 
functional hearing groups. The mid-frequency cetacean group includes 
beluga whales and was derived based on beluga whale data, as data from 
nine beluga whales was used in creating the composite audiogram in the 
NMFS Acoustic Guidance. The paper cited by CBD (Mooney et al, 2018) 
does not illustrate a particular portion of beluga whale hearing range 
that has been mischaracterized; rather, that paper highlights the 
amount of variation in hearing sensitivity across individuals within a 
population. The paper concludes that testing auditory evoked potentials 
of several individuals in a population is necessary to accurately 
describe sensitivity and variance in hearing. NMFS agrees that these 
pieces of information would be crucial in quantifying the sensitivity 
of Cook Inlet beluga whales, but currently this data does not exist. 
NMFS uses the best available science in the form of the Acoustic 
Guidance to determine potential onset of PTS and TTS. Aside from our 
acoustic thresholds, NMFS can only qualitatively consider the 
sensitivity of beluga whales to anthropogenic sounds, particularly in 
light of the potentially high variance in sensitivity across 
individuals. Because of this uncertainty and lack of data on the 
sensitivity for the Cook Inlet stock of beluga whales, NMFS is 
requiring Hilcorp to shut down activities when any beluga is sighted 
within the relevant Level B harassment isopleth.
    Regarding density, NMFS carried two potential densities all the way 
through the analysis--the first based purely on the NMFS summer aerial 
surveys mentioned in CBD's comment letter, and the second using the 
aerial surveys as the basis for a model that accounts for beluga whale 
presence as well as beluga whale count data. While the data is 
collected in the summer, this is the best scientific information 
available. Rigorous surveys for Cook Inlet beluga whales outside of 
summer months are not considered feasible, largely due to safety 
concerns because of weather conditions. Monitoring reports of previous 
incidental take authorizations issued in Cook Inlet with take of Cook 
Inlet beluga whales reveal that sightings of Cook Inlet beluga whales 
are often substantially lower than the calculated exposure estimate or 
take authorized. This data, couple with the beluga-specific mitigation 
measures included in this rule, suggest that take of Cook Inlet belugas 
is not underestimated.
    Comment 35: The CBD commented that NMFS relies on avoidance to make 
its negligible impact determination, while ignoring that avoidance can 
be a detrimental behavior.
    Response: NMFS does not rely on avoidance behaviors to make its 
negligible impact determination. NMFS agrees that avoidance of 
preferred habitat may temporarily limit optimal feeding or other 
biologically important behaviors. However, the majority of the proposed 
activities will occur in habitat that is not known to be of particular 
significance to Cook Inlet beluga whales. For those activities that are 
conducted near habitat thought to be important to beluga whale behavior 
such as mud flats in the Susitna River Delta, a time-area closure will 
be implemented so beluga whales will be able to access this habitat 
during the summer, which is when they frequent upper Cook Inlet. In 
combination, the density of Cook Inlet beluga whales in the area of the 
activity, which inform the take estimation, coupled with mitigation and 
monitoring measures and knowledge of the range of Cook Inlet beluga 
whales during the months of operation proposed by Hilcorp, suggest a 
finding of negligible impact of these effects on Cook Inlet beluga 
whales.
    Comment 36: The CBD commented that NMFS should count all exposures 
as separate takes, and that counting all exposures of an animal that 
occur within one day as one take is an underestimate.
    Response: For the purposes of consistency in estimating the numbers 
of takes, we do not consider one individual as taken more than one time 
in a day, even if modeling or direct knowledge might show that an 
individual would likely be exposed to sound or other stressors in a 
manner that we would consider a take multiple separate times in one 
day. For the

[[Page 37458]]

purposes of analyzing the impacts of these takes to the stock, it is 
important to understand the likely nature of these instances of take 
within a day (e.g., momentary exposure versus multiple hours, high 
level versus low level of intensity of acoustic exposure). We 
acknowledge that certain harbor seals are likely to swim in and out of 
a potentially ensonified area without remaining in the ensonified zone 
for the entire daily duration of an activity. Also, of note, just 
because activities continue for hours at a time, that does not mean 
that mobile marine mammals are exposed (to sometimes mobile sources) 
for all of those hours, as in many cases they would be expected to move 
away. While certain species, such as Cook Inlet beluga whales, Steller 
sea lions, and harbor seals, are known to exhibit site fidelity, 
Hilcorp's activities are not planned to occur directly in biologically 
important habitat for any of these marine mammal species in Cook Inlet. 
Therefore, site fidelity may not automatically equate to increased 
duration of exposure, especially given the use of mobile sources, as 
the habitat that animals are likely to frequent, such as important 
haulouts or river mouths, are near the activity, but primarily are 
outside of the calculated acoustic isopleths. NMFS requires that data 
be collected on the number of animals that are taken and the frequency 
of takes. While NMFS does not anticipate that multiple Level B 
harassments of the same animal within 2 hours would substantively alter 
the fitness of that animal, NMFS would request that the frequency of 
those takes is reported. However, in certain environments or 
circumstances, such as the use of a mobile source where an individual 
of a certain species is sighted, not sighted for a number of hours, and 
sighted again, it is unlikely that, without substantial uniquely 
identifiable markings, a PSO would know they are sighting a repeat 
individual. Therefore, in most instances, these sightings would be 
reported as separate takes during the activity.
    Comment 37: The CBD commented that NMFS must consider the best 
available scientific information regarding noise and marine mammals, 
noting some sources in the proposed rule are decades old. The CBD also 
commented that NMFS overlooked particularly important references 
regarding sensitivity of marine mammals to airgun sounds, citing Miller 
at al. (2005) and Gomez et al. (2016).
    Response: NMFS has considered the best available science in this 
rulemaking. Certain papers, particularly papers pertaining to basic 
physiolology, biology, and acoustics, formed a baseline knowledge that 
is expanded upon in recent publications. However, the age of certain 
papers does not negate their validity or quality of science. As 
appropriate, NMFS considers the best available science and consistently 
reviews recent literature to inform our analyses. While the papers 
cited by CBD are part of the general body of literature regarding 
marine mammals and anthropogenic noise, they each present shortcomings. 
The Miller et al (2005) paper is a case study of a marine seismic 
survey in Canadian waters of the Beaufort Sea. Beluga whales were 
recorded during this study with potential avoidance behaviors recorded 
at various distances. NMFS does not dispute that avoidance is a 
potential outcome of seismic activity, as discussed in our Effects on 
Marine Mammals section below. However, the conclusion of the Miller et 
al (2005) paper states that the mitigation measures undertaken during 
the survey, many of which are similar to measures required in this 
rulemaking, were found to be effective. Additionally, the results of 
the Gomez et al (2016) paper, suggest that, for the studies reviewed in 
this paper, received level did not explain the severity of the 
behavioral response to anthropogenic sound sources. For some sources, 
including seismic sources, it is possible that distance to the source 
may have a more direct relationship to a behavioral response than the 
received level. Gomez et al (2016) ultimately concluded there were 
insufficient data to identify a dose-response relationship between 
received level and severity of behavioral response. This supports NMFS' 
analysis that there is uncertainty in the severity and type of response 
that animals may exhibit in response to Hilcorp's activities. However, 
to minimize impacts to the best of our ability, NMFS is implementing 
mitigation measures in line with those found to be effective in Miller 
et al (2005). Time-area closures at areas and times of biological 
importance, airgun shutdowns, and ramp-up of airguns are all measures 
that are discussed in the paper and that are required in this rule.
    Comment 38: The CBD commented that the negligible impact statement 
does not consider: Above-water impacts to seals and sea lions that are 
hauled out, risk of ship strike from non-source project vessels, 
entanglement from seismic survey cables, and increased risk of oil 
spills from the activities.
    Response: NMFS does not consider above-water acoustic impacts to 
seals and sea lions in this rulemaking because none are expected, as 
described in the description of Iniskin Peninsula activities above. 
None of the proposed activities are likely to result in take from 
above-water acoustic disturbance in the vicinity of hauled out seals 
and sea lions, as any animals potentially exposed to those sounds above 
water would also be exposed to underwater sound that rises to the level 
of take. Additionally, takes of marine mammals due to ship strike from 
non-source project vessels is not considered because it is not 
anticipated or authorized, as described in the proposed rule section 
titled Ship Strike. All project vessels and non-Hilcorp project vessels 
are subject to maritime regulations, and take of marine mammals due to 
ship strike is not authorized. Oil spills are not considered because 
take of marine mammals due to oil spills are not anticipated or 
authorized. Hilcorp is required to comply with all regulations related 
to oil drilling and is responsible for ensuring its compliance with 
those regulations. An oil spill, or a violation of other federal 
regulations, is not authorized under this rule. Entanglements in 
Hilcorp's streamers are also not authorized. While seismic streamers 
can extend a kilometer or farther behind the source vessel, Hilcorp 
employs a chase vessel behind the streamers to monitor and prevent 
potential entanglement hazards, primarily entanglement of other 
vessels. No entanglement events from seismic streamer equipment have 
been previously reported to NMFS.
    Comment 39: The CBD commented that NMFS is authorizing more than 
small numbers of takes of marine mammals due to Hilcorp's activity.
    Response: As described in NMFS' Notice of Issuance of Final IHA (83 
FR 63268; December 7, 2018), NMFS established that one-third of the 
individuals of the most appropriate population abundance number--as 
compared with the assumed number of individuals taken--is an 
appropriate limit with regard to ``small numbers.'' NMFS proposed to 
authorize a smaller proportion of takes than one third of the 
inividuals in a stock, the highest of which is 25% for the Cook Inlet 
stock of harbor seals. As described in the Take Estimation section 
below, this authorized number of instances of take is likely an 
overestimate of the number of individuals taken, but was used to 
support our small numbers finding nonetheless. For Cook Inlet beluga 
whales, the authorized take, by Level B harassment only, accounts for 
11 percent of the population annually, which NMFS also considers small.
    Comment 40: The CBD commented that NMFS' definition of small 
numbers is conflated with the negligible impact

[[Page 37459]]

requirement by defining small numbers relative to the overall 
population.
    Response: The small numbers finding and negligible impact 
determination are separate findings and must both be made for this 
rulemaking. NMFS disagrees that our definitions are duplicative in 
nature. The small numbers finding is based purely on the numbers of 
individuals taken relative to the stock or population abundance, 
whether that information is quantitative or qualitative. The negligible 
impact determination considers relevant biological and contextual 
factors, i.e., the anticipated impacts to the individuals and the 
stock, of the take authorized. Please see the Notice of Issuance of 
Final IHA (83 FR 63268), which includes a full discussion of NMFS' 
rationale regarding how the agency should implement the MMPA small 
numbers standard and, therefore, addresses the commenter's issues.
    Comment 41: The CBD commented that the small numbers determination 
is flawed, as there are instances in which estimated exposures are 
higher than authorized take, particularly for Cook Inlet beluga whales 
and harbor seals.
    Response: The small numbers finding is based on the number of 
individuals proposed to be taken relative to the population size. As 
described in the Estimated Take section below, particularly for harbor 
seals, NMFS expects multiple exposures of the same individuals, but 
does not expect 40 percent of the individuals in the entire population 
to be taken during activity. Based on the range and site fidelity of 
harbor seals, it is implausible that such a large proportion of the 
total population would be behaviorally disturbed to the point of Level 
B harassment during Hilcorp's temporally and spatially limited 
activities. Additionally, despite the calculations for the exposure 
estimate, as required in our reporting measures, once the authorized 
number of takes has been reached, the activity must cease. Therefore, 
NMFS made the small numbers finding based on the number of takes of 
individuals authorized. In this case, NMFS will authorize 11,784 
instances of exposure of harbor seals; however, based on factors 
described in the Take Estimation section below, we do not expect the 
estimated exposures to result in take of more than 25 percent of the 
population. Please see the Notice of Issuance of Final IHA (83 FR 
63268) for a full discussion of NMFS' rationale regarding how the 
agency should implement the MMPA small numbers standard.
    Comment 42: The CBD commented that the proposed activities will 
have an unmitigable adverse impact on the availability of Cook Inlet 
belugas for subsistence use.
    Response: NMFS disagrees with this assertion. As described in the 
Least Practicable Adverse Impact section below, a moratorium on 
subsistence hunting of Cook Inlet belugas has been in place for over 10 
years. The criteria established for when subsistence hunt of Cook Inlet 
beluga could resume included the need for a ten year average abundance 
estimate to exceed 350 animals, as well as a requirement for an 
increasing population trajectory; therefore, there are no active 
subsistence uses of beluga whales that the activity could interfere 
with.
    Comment 43: The CBD commented that NMFS failed to ensure the least 
practicable adverse impact. This included failing to consider 
alternative mitigation measures to reduce impacts of the activities, 
including reducing activities in all biologically important areas and 
utilizing PAM.
    Response: In the proposed rule, NMFS described its consideration of 
passive acoustic monitoring and described previous attempts to use PAM 
in previous geophysical surveys in Cook Inlet. These attempts have not 
been successful, and NMFS has elected to not require further attempts 
of PAM at this time. Instead, NMFS has chosen to require a mitigation 
vessel for extended visual observation coverage, as well as aerial 
surveys specifically directed at searching for Cook Inlet beluga whales 
during seismic activity. Based on the intended purpose of Hilcorp's 
activities and the locations of certain project sets, it was not 
practicable to exclude all biologically important areas (BIAs) for Cook 
Inlet beluga whales from Hilcorp's action area. NMFS is required to 
analyze what was proposed by Hilcorp, which included oil and gas 
activities at specific lease sale sites that lie within Cook Inlet 
beluga whale BIAs. However, NMFS has continued to require a seasonal 
exclusion zone at the Susitna River Delta to protect essential critical 
habitat for Cook Inlet beluga whales. Additionally, NMFS has added an 
additional closure during seismic surveying at the mouth of the Kasilof 
River, which is also part of the Cook Inlet beluga whale BIA, from 
January 1 to May 31. No other BIAs for marine mammals are designated in 
Cook Inlet or in Hilcorp's action area. The next closest BIA, which is 
located south of the Kachemak Peninsula, is for fin whales.
    Comment 44: The CBD commented that the purpose and need of the EA 
are too narrowly defined.
    Response: The EA evaluates the impacts of issuing an incidental 
take authorization for the take of marine mammals. As described in the 
EA (and described in the context of the MMPA in the proposed rule) and 
summarized in the FONSI, the effects of the marine mammal take 
anticipated and authorized will not significantly impact the quality of 
the human environment.
    Comment 45: The CBD commented that NMFS failed to consider a 
reasonable range of alternatives, as the alternatives considered in the 
EA did not contain additional monitoring beyond that considered in the 
proposed rule.
    Response: NMFS considered several alternatives, including 
additional mitigation measures that are not required in this final 
rule. In accordance with NEPA and CEQ Regulations, NMFS, to the fullest 
extent possible, integrates the requirements of NEPA with other 
regulatory processes required by law and by agency practice, so that 
all procedures run concurrently, rather than consecutively. 
Accordingly, while the EA considered two designated alternatives 
(issuance or non-issuance of the rule and LOAs), additional mitigation 
alternatives were considered in the rule issuance process. For example, 
some of the potential mitigation measures, discussed further below, 
were included in the proposed rule with our rationale for not proposing 
to require these mitigation measures (i.e. multiple unsuccessful 
deployments of several types of PAM). Because of the limited success of 
certain monitoring technologies such as PAM and night vision in Cook 
Inlet, NMFS did not find additional reasonable alternatives to carry 
through the analysis in the EA. However, the requirements in this final 
rule include mitigation beyond what was proposed by Hilcorp and what 
was presented in the proposed rule, as an additional mitigation vessel 
with at least one on-duty PSO is now required during seismic activity.
    Comment 46: The CBD commented that the EA's affected environment 
sections, including sections on marine mammal habitat, biological 
environment, and socioeconomic development, are incomplete.
    Response: Further detail has been added to these sections in the 
final EA.
    Comment 47: The CBD commented that the draft EA did not include 
sufficient detail on impacts to marine mammal habitat, including 
critical habitat for ESA-listed marine mammals.
    Response: Additional detail has been added to the relevant sections 
in the final EA.

[[Page 37460]]

    Comment 48: The CBD commented that description of potential effects 
of the proposed action on marine mammals in the EA is deficient, 
including insufficient discussion of behavioral and physiological 
impacts. Effects on prey species were also noted to be lacking.
    Response: The discussion of potential effects to marine mammals and 
their prey species has been expanded in the Final EA.
    Comment 49: The CBD commented that the EA does not address 
potential impacts to subsistence uses. The CBD stated that removal of 
one animal from the Cook Inlet beluga whale population has a population 
level effect. The CBD also noted that lack of spatial overlap between 
the proposed activities and subsistence hunted animals does not 
alleviate concerns about availability for subsistence uses.
    Response: NMFS considered potential impacts to subsistence uses of 
marine mammals in Section 3.3.1 of the Final EA. NMFS does not solely 
rely on lack of spatial overlap to conclude the activities are unlikely 
to have effects on subsistence use. In our proposed rule, we described 
the history of subsistence hunting of Cook Inlet beluga whales and 
explained why it is unlikely that subsistence hunting for Cook Inlet 
beluga whales will resume over the next five years. Additionally, the 
number of individual harbor seals likely to be taken by Hilcorp's 
activities would primarily be taken by Level B harassment. While harbor 
seals may temporarily be displaced due to certain coastal construction 
such as the causeway construction, most of Hilcorp's work will not 
occur onshore and will not displace harbor seals from land-based 
haulouts where they can be hunted or prevent hunters from approaching 
hauled out animals. The land-based work will not occur at known harbor 
seal haulouts and will not prevent hunters from pursuing seals at 
haulouts. NMFS is not authorizing any serious injury or mortality, or 
any other take that could potentially be considered a removal from the 
population.
    Comment 50: The CBD commented that certain aspects were lacking in 
the cumulative effects section of the EA. They commented that NMFS 
should include a proposed nationwide five-year leasing program and 
potential additional oil and gas activity in Cook Inlet. They commented 
that spill related-effects or effects of other disasters at Pebble Mine 
are not considered. They also noted discussion of Alaska LNG's proposed 
work and the Alaska Gasline Development Corporation's plans for a 
pipeline was missing from the cumulative effects section.
    Response: NMFS thanks CBD for raising the Alaska LNG and pipeline 
development activities as projects that should be included in the 
Cumulative Impacts section of the EA. They have been added accordingly. 
The proposed leasing program was not included in the EA as activity 
that could directly affect marine mammals, their habitat, or their 
prey, as it is not expected to occur in the foreseeable future. 
Particularly in Cook Inlet, a lease sale does not always translate to 
immediate drilling or other geophysical testing in the lease blocks. It 
would be appropriate to consider these activities once the leases have 
been granted. Additionally, oil spills or other disasters stemming from 
man-made structures in Cook Inlet are not considered, as they are not 
authorized and are a breach of regulations. It is the responsibility of 
the applicants to comply with all additional regulations, and to work 
with the state to obtain approval of their Oil Discharge Prevention and 
Contingency Plans (ODPCP).
    Comment 51: The CBD commented that the EA failed to quantify 
greenhouse gas emissions of drilling and production and the impacts of 
continued use of oil platforms beyond their intended lifespan.
    Response: NMFS does not quantify greenhouse gas emissions from 
drilling, as this is outside the scope of our assessment. The amount 
and extent of drilling by Hilcorp is unknown, and the drilling activity 
itself is not authorized by NMFS under the MMPA. Additionally, use of 
drill rigs beyond their lifespan is not a practice that is authorized 
or condoned by NMFS, and is therefore not considered to be likely in 
the foreseeable future.

Description of Marine Mammals in the Area of Specified Activities

    Eleven species of marine mammal have the potential to occur in the 
action area during the five year period of activities conducted by 
Hilcorp. These species are described in further detail below.
    Table 2 lists all species with expected potential for occurrence in 
Cook Inlet and summarizes information related to the population or 
stock, including regulatory status under the MMPA and ESA and potential 
biological removal (PBR), where known. For taxonomy, we follow 
Committee on Taxonomy (2016). PBR is defined by the MMPA as the maximum 
number of animals, not including natural mortalities, that may be 
removed from a marine mammal stock while allowing that stock to reach 
or maintain its optimum sustainable population (as described in NMFS' 
SARs). While no mortality is anticipated or authorized here, PBR and 
annual serious injury and mortality from anthropogenic sources are 
included here as gross indicators of the status of the species and 
other threats.
    Marine mammal abundance estimates presented in this document 
represent the total number of individuals that make up a given stock or 
the total number estimated within a particular study or survey area. 
NMFS' stock abundance estimates for most species represent the total 
estimate of individuals within the geographic area, if known, that 
comprises that stock. For some species, this geographic area may extend 
beyond U.S. waters. All managed stocks in this region are assessed in 
NMFS' 2017 U.S. Alaska and Pacific SARs (Muto et al, 2017; Carretta et 
al, 2017). All values presented in Table 2 are the most recent 
available at the time of publication and are available in the 2017 SARs 
and draft 2018 SARs (available online at: https://www.fisheries.noaa.gov/action/2018-draft-marine-mammal-stock-assessment-reports-available).

                                           Table 2--Species With the Potential To Occur in Cook Inlet, Alaska
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                             Stock abundance (CV,
                                                                                         ESA/MMPA status;      Nmin, most recent               Annual M/
             Common name                  Scientific name               Stock            strategic (Y/N) 1    abundance survey) 2      PBR        SI 3
 
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                          Order Cetartiodactyla--Cetacea--Superfamily Mysticeti (baleen whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Eschrichtiidae:
    Gray whale......................  Eschrichtius robustus..  Eastern Pacific........  -/-; N              20,990 (0.05, 20,125,         624       4.25
                                                                                                             2011).

[[Page 37461]]

 
Family Balaenopteridae (rorquals):
    Fin whale.......................  Balaenoptera physalus..  Northeastern Pacific...  E/D; Y              3,168 (0.26,2,554             5.1        0.4
                                                                                                             2013).
    Minke whale.....................  Balaenoptera             Alaska.................  -/-; N              N/A...................        N/A          0
                                       acutorostrata.
    Humpback whale..................  Megaptera novaeangliae.  Western North Pacific..  E/D; Y              1,107 (0.3, 865, 2006)          3        3.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                            Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Delphinidae:
    Beluga whale....................  Delphinapterus leucas..  Cook Inlet.............  E/D; Y              312 (0.1, 287, 2014)..       0.54       0.57
    Killer whale....................  Orcinus orca...........  Alaska Resident........  -/-; N              2,347 (N/A, 2,347,             24          1
                                                                                                             2012).
                                                               Alaska Transient.......  -/-; N              587 (N/A, 587, 2012)..        5.9          1
Family Phocoenidae (porpoises):
    Harbor porpoise.................  Phocoena phocoena......  Gulf of Alaska.........  -/-; Y              31,046 (0.214, N/A,         Undet         72
                                                                                                             1998).
    Dall's porpoise.................  Phocoenoides dalli.....  Alaska.................  -/-; N              83,400 (0.097, N/A,         Undet         38
                                                                                                             1993).
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         Order Carnivora--Superfamily Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Otariidae (eared seals and
 sea lions):
    Steller sea lion................  Eumetopias jubatus.....  Western................  E/D; Y              53,303 (N/A, 53,303,          320        241
                                                                                                             2016).
    California sea lion.............  Zalophus californianus.  U.S....................  -/-; N              296,750 (153,337, N/A,      9,200        331
                                                                                                             2011).
Family Phocidae (earless seals):
    Harbor seal.....................  Phoca vitulina.........  Cook Inlet/Shelikof....  -/-; N              27,386 (25,651, N/A,          770        234
                                                                                                             2011).
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed
  under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality
  exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed
  under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
2 NMFS marine mammal stock assessment reports online at: www.nmfs.noaa.gov/pr/sars/. CV is coefficient of variation; Nmin is the minimum estimate of
  stock abundance. In some cases, CV is not applicable [explain if this is the case]
3 These values, found in NMFS' SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g., commercial
  fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated
  with estimated mortality due to commercial fisheries is presented in some cases.

Fin Whales
    For management purposes, three stocks of fin whales are currently 
recognized in U.S. Pacific waters: Alaska (Northeast Pacific), 
California/Washington/Oregon, and Hawaii. Recent analyses provide 
evidence that the population structure should be reviewed and possibly 
updated. However, substantially new data on the stock structure is 
lacking (Muto et al 2017). Fin whales, including the Northeastern 
Pacific stock, are listed as endangered under the ESA.
    Mizroch et al. (2009) provided a comprehensive summary of fin whale 
sightings data, including whaling catch data and determined there could 
be at least six populations of fin whales. Evidence suggests two 
populations are migratory (eastern and western North Pacific) and two 
to four more are year-round residents in peripheral seas such as the 
Gulf of California, East China Sea, Sanriku-Hokkaido, and possibly the 
Sea of Japan. The two migratory stocks are likely mingling in the 
Bering Sea in July and August. Moore et al. (1998, 2006), Watkins et 
al. (2000), and Stafford et al. (2007) documented high rates of calling 
along the Alaska coast beginning in August/September and lasting 
through February. Fin whales are regularly observed in the Gulf of 
Alaska during the summer months, even though calls are seldom detected 
during this period (Stafford et al. 2007). Instruments moored in the 
southeast Bering Sea detected calls over the course of a year and found 
peaks from September to November as well as in February and March 
(Stafford et al. 2010). Delarue et al. (2013) detected calls in the 
northeastern Chukchi Sea from instruments moored from July through 
October from 2007 through 2010.
    Fin whales are found seasonally in the Gulf of Alaska, Bering Sea, 
and as far north as the northern Chukchi Sea (Muto et al. 2017). 
Surveys conducted in coastal waters of the Aleutians and the Alaska 
Peninsula found that fin whales occurred primarily from the Kenai 
Peninsula to the Shumagin Islands and were abundant near the Semidi 
Islands and Kodiak Island (Zerbini et al. 2006). An opportunistic 
survey conducted on the shelf of the Gulf of Alaska found fin whales 
concentrated west of Kodiak Island in Shelikof Strait, and in the 
southern Cook Inlet region. Smaller numbers were also observed over the 
shelf east of Kodiak to Prince William Sound (AFSC, 2003). In the 
northeastern Chukchi Sea, visual sightings and acoustic detections have 
been increasing, which suggests the stock may be re-occupying habitat 
used prior to large-scale commercial whaling (Muto et al. 2017). Most 
of these areas are feeding habitat for fin whales. Fin whales are 
rarely observed in Cook Inlet, and most sightings occur near the 
entrance of the inlet. During the NMFS aerial surveys in Cook Inlet 
from 2000-2016, 10 sightings of 26 estimated individual fin whales in 
lower Cook Inlet were observed (Shelden et al. 2013, 2015, 2016).
Humpback Whales
    Currently, three populations of humpback whales are recognized in 
the North Pacific, migrating between their respective summer/fall 
feeding areas and winter/spring calving and mating areas as follows 
(Baker et al. 1998; Calambokidis et al. 1997). Although there is 
considerable distributional overlap in the humpback whale stocks that 
use Alaska, the whales seasonally found in lower Cook Inlet are 
probably of the Central North Pacific stock (Muto et al. 2017). Listed 
as endangered under the ESA, this stock has recently been estimated at 
7,890 animals (Muto et al. 2017). The Central North Pacific stock 
winters in Hawaii and summers from

[[Page 37462]]

British Columbia to the Aleutian Islands (Calambokidis et al. 1997), 
including Cook Inlet.
    Humpback whales in the high latitudes of the North Pacific Ocean 
are seasonal migrants that feed on euphausiids and small schooling 
fishes (Muto et al. 2017). During the spring, these animals migrate 
north and spend the summer feeding in the prey-rich sub-polar waters of 
southern Alaska, British Columbia, and the southern Chukchi Sea. 
Individuals from the Western North Pacific (endangered), Hawaii (not 
listed under the ESA), and the Mexico (threatened) DPSs migrate to 
areas near and potentially in the Petition region. However, most of the 
individuals that migrate to the Cook Inlet area are likely from the 
Hawaii DPS and not the Western North Pacific or Mexico DPSs (NMFS 
2017).
    In the summer, humpback whales are regularly present and feeding in 
the Cook Inlet region, including Shelikof Strait, Kodiak Island bays, 
and the Barren Islands, in addition to Gulf of Alaska regions adjacent 
to the southeast side of Kodiak Island (especially Albatross Banks), 
the Kenai and Alaska peninsulas, Elizabeth Island, as well as south of 
the Aleutian Islands. Humpbacks also may be present in some of these 
areas throughout autumn (Muto et al. 2017). Humpback whales have been 
observed during marine mammal surveys conducted in Cook Inlet. However, 
their presence is largely confined to lower Cook Inlet. Recent 
monitoring by Hilcorp in upper Cook Inlet has also included 3 humpback 
whale sightings near Tyonek (Sitkiewicz et al. 2018). During 
SAExploration's 2015 seismic program, three humpback whales were 
observed in Cook Inlet; two near the Forelands and one in Kachemak Bay 
(Kendall et al. 2015). During NMFS' Cook Inlet beluga whale aerial 
surveys from 2000-2016, there were 88 sightings of 191 estimated 
individual humpback whales in lower Cook Inlet (Shelden et al. 2017). 
They have been regularly seen near Kachemak Bay during the summer 
months (Rugh et al. 2005). There are observations of humpback whales as 
far north as Anchor Point, with recent summer observations extending to 
Cape Starichkof (Owl Ridge 2014). Although several humpback whale 
sightings occurred mid-inlet between Iniskin Peninsula and Kachemak 
Bay, most sightings occurred outside of the Petition region near 
Augustine, Barren, and Elizabeth Islands (Shelden et al. 2013, 2015, 
2017).
    Ferguson et al. (2015) has established Biologically Important Areas 
(BIAs) as part of the NOAA Cetacean Density and Distribution Mapping 
Working Group (CetMap) efforts. This information supplements the 
quantitative information on cetacean density, distribution, and 
occurrence by: (1) Identifying areas where cetacean species or 
populations are known to concentrate for specific behaviors, or be 
range-limited, but for which there is not sufficient data for their 
importance to be reflected in the quantitative mapping effort; and (2) 
providing additional context within which to examine potential 
interactions between cetaceans and human activities. A ``Feeding Area'' 
BIA for humpback whales in the Gulf of Alaska region encompasses the 
waters east of Kodiak Island (the Albatross and Portlock Banks), a 
target for historical commercial whalers based out of Port Hobron, 
Alaska (Ferguson et al. 2015; Reeves et al. 1985; Witteveen et al. 
2007). This BIA also includes waters along the southeastern side of 
Shelikof Strait and in the bays along the northwestern shore of Kodiak 
Island. The highest densities of humpback whales around the Kodiak 
Island BIA occur from July-August (Ferguson et al. 2015).
Minke Whale
    Minke whales are most abundant in the Gulf of Alaska during summer 
and occupy localized feeding areas (Zerbini et al. 2006). 
Concentrations of minke whales have occurred along the north coast of 
Kodiak Island (and along the south coast of the Alaska Peninsula 
(Zerbini et al. 2006). The current estimate for minke whales between 
Kenai Fjords and the Aleutian Islands is 1,233 individuals (Zerbini et 
al. 2006). During shipboard surveys conducted in 2003, three minke 
whale sightings were made, all near the eastern extent of the survey 
from nearshore Prince William Sound to the shelf break (NMML 2003).
    Minke whales become scarce in the Gulf of Alaska in fall; most 
whales are thought to leave the region by October (Consiglieri et al. 
1982). Minke whales are migratory in Alaska, but recently have been 
observed off Cape Starichkof and Anchor Point year-round (Muto et al. 
2017). During Cook Inlet-wide aerial surveys conducted from 1993 to 
2004, minke whales were encountered three times (1998, 1999, and 2006), 
both times off Anchor Point 16 miles northwest of Homer (Shelden et al. 
2013, 2015, 2017). A minke whale was also reported off Cape Starichkof 
in 2011 (A. Holmes, pers. comm.) and 2013 (E. Fernandez and C. 
Hesselbach, pers. comm.), suggesting this location is regularly used by 
minke whales, including during the winter. Several minke whales were 
recorded off Cape Starichkof in early summer 2013 during exploratory 
drilling (Owl Ridge 2014), suggesting this location is regularly used 
by minke whales year-round. During Apache's 2014 survey, a total of 2 
minke whale groups (3 individuals) were observed during this time 
period, one sighting to the southeast of Kalgin Island and another 
sighting near Homer (Lomac-MacNair et al. 2014). SAExploration noted 
one minke whale near Tuxedni Bay in 2015 (Kendall et al. 2015). This 
species is unlikely to be seen in upper Cook Inlet but may be 
encountered in the mid and lower Inlet.
Killer Whales
    Two different stocks of killer whales inhabit the Cook Inlet region 
of Alaska: The Alaska Resident Stock and the Gulf of Alaska, Aleutian 
Islands, Bering Sea Transient Stock (Muto et al 2017). Seasonal and 
year-round occurrence has been noted for killer whales throughout 
Alaska (Braham and Dahlheim 1982), where whales have been labeled as 
``resident,'' ``transient,'' and ``offshore'' type killer whales 
(Dahlheim et al. 2008; Ford et al. 2000). The killer whales using Cook 
Inlet are thought to be a mix of resident and transient individuals 
from two different stocks: The Alaska Resident Stock, and the Gulf of 
Alaska, Aleutian Islands, and Bering Sea Transient Stock (Allen and 
Angliss 2015). Although recent studies have documented movements of 
Alaska Resident killer whales from the Bering Sea into the Gulf of 
Alaska as far north as southern Kodiak Island, none of these whales 
have been photographed further north and east in the Gulf of Alaska 
where regular photo-identification studies have been conducted since 
1984 (Muto et al. 2017).
    Killer whales are occasionally observed in lower Cook Inlet, 
especially near Homer and Port Graham (Shelden et al. 2003; Rugh et al. 
2005). The few whales that have been photographically identified in 
lower Cook Inlet belong to resident groups more commonly found in 
nearby Kenai Fjords and Prince William Sound (Shelden et al. 2003). The 
availability of these prey species largely determines the likeliest 
times for killer whales to be in the area. During aerial surveys 
conducted between 1993 and 2004, killer whales were observed on only 
three flights, all in the Kachemak and English Bay area (Rugh et al. 
2005). However, anecdotal reports of killer whales feeding on belugas 
in upper Cook Inlet began increasing in the 1990s, possibly in response 
to declines in sea lion and harbor seal prey elsewhere (Shelden et al. 
2003). One killer whale group of two individuals was observed during 
the 2015

[[Page 37463]]

SAExploration seismic program near the North Foreland (Kendall et al. 
2015). During NMFS aerial surveys, killer whales were observed in 1994 
(Kamishak Bay), 1997 (Kachemak Bay), 2001 (Port Graham), 2005 (Iniskin 
Bay), 2010 (Elizabeth and Augustine Islands), and 2012 (Kachemak Bay; 
Shelden et al. 2013). Eleven killer whale strandings have been reported 
in Turnagain Arm, six in May 1991, and five in August 1993. This 
species is expected to be rarely seen in upper Cook Inlet but may be 
encountered in the mid and lower Inlet.
Gray Whales
    Gray whales have been reported feeding near Kodiak Island, in 
southeastern Alaska, and south along the Pacific Northwest (Allen and 
Angliss 2013). Because most gray whales migrating through the Gulf of 
Alaska region are thought to take a coastal route, BIA boundaries for 
the migratory corridor in this region were defined by the extent of the 
continental shelf (Ferguson et al. 2015).
    Most gray whales calve and breed from late December to early 
February in protected waters along the western coast of Baja 
California, Mexico. In spring, the ENP stock of gray whales migrates 
approximately 8,000 km (5,000 mi) to feeding grounds in the Bering and 
Chukchi seas before returning to their wintering areas in the fall 
(Rice and Wolman 1971). Northward migration, primarily of individuals 
without calves, begins in February; some cow/calf pairs delay their 
departure from the calving area until well into April (Jones and Swartz 
1984). An unusual mortality event (UME) has been declared for gray 
whales along the Pacific coast, including Alaska. As of June 6, 2019, 
six gray whales have stranded in Alaska in 2019. The cause of the UME 
is not known at the time of writing; while a subset of necropsied 
individuals appear to be emaciated, this observation is not consistent 
across all strandings in the UME.
    Gray whales approach the action area in late March, April, May, and 
June, and leave again in November and December (Consiglieri et al. 
1982; Rice and Wolman 1971) but migrate past the mouth of Cook Inlet to 
and from northern feeding grounds. Some gray whales do not migrate 
completely from Baja to the Chukchi Sea but instead feed in select 
coastal areas in the Pacific Northwest, including lower Cook Inlet 
(Moore et al. 2007). Most of the population follows the outer coast of 
the Kodiak Archipelago from the Kenai Peninsula in spring or the Alaska 
Peninsula in fall (Consiglieri et al. 1982; Rice and Wolman 1971). 
Though most gray whales migrate past Cook Inlet, small numbers have 
been noted by fishers near Kachemak Bay, and north of Anchor Point 
(BOEM 2015). During the NMFS aerial surveys, gray whales were observed 
in the month of June in 1994, 2000, 2001, 2005 and 2009 on the east 
side of Cook Inlet near Port Graham and Elizabeth Island but also on 
the west side near Kamishak Bay (Shelden et al. 2013). One gray whale 
was sighted as far north at the Beluga River. Additionally, summering 
gray whales were seen offshore of Cape Starichkof by marine mammal 
observers monitoring Buccaneer's Cosmopolitan drilling program in 2013 
(Owl Ridge 2014). During Apache's 2012 seismic program, nine gray 
whales were observed in June and July (Lomac-MacNair et al. 2013). 
During Apache's seismic program in 2014, one gray whale was observed 
(Lomac-MacNair et al. 2014). During SAExploration's seismic survey in 
2015, no gray whales were observed (Kendall et al. 2015). This species 
is unlikely to be seen in upper Cook Inlet but may be encountered in 
the mid and lower Inlet.
Cook Inlet Beluga Whales
    The Cook Inlet beluga whale DPS is a small geographically isolated 
population that is separated from other beluga populations by the 
Alaska Peninsula. The population is genetically distinct from other 
Alaska populations suggesting the peninsula is an effective barrier to 
genetic exchange (O'Corry-Crowe et al. 1997). The Cook Inlet beluga 
whale population is estimated to have declined from 1,300 animals in 
the 1970s (Calkins 1989) to about 340 animals in 2014 (Shelden et al. 
2015). The precipitous decline documented in the mid-1990s was 
attributed to unsustainable subsistence practices by Alaska Native 
hunters (harvest of >50 whales per year) (Mahoney and Shelden 2000). In 
2006, a moratorium to cease hunting was agreed upon to protect the 
species. In April 2011, NMFS designated critical habitat for the beluga 
under the ESA (76 FR 20180) as shown on Figure 13 of the application. 
NMFS finalized the Conservation Plan for the Cook Inlet beluga in 2008 
(NMFS 2008a). NMFS finalized the Recovery Plan for Cook Inlet beluga 
whales in 2016 (NMFS 2016a).
    The Cook Inlet beluga stock remains within Cook Inlet throughout 
the year (Goetz et al. 2012a). Two areas, consisting of 7,809 km\2\ 
(3,016 mi\2\) of marine and estuarine environments considered essential 
for the species' survival and recovery were designated critical 
habitat. However, in recent years the range of the beluga whale has 
contracted to the upper reaches of Cook Inlet because of the decline in 
the population (Rugh et al. 2010). Area 1 of the Cook Inlet beluga 
whale critical habitat encompasses all marine waters of Cook Inlet 
north of a line connecting Point Possession (61.04[deg] N, 150.37[deg] 
W) and the mouth of Three Mile Creek (61.08.55[deg] N, 151.04.40[deg] 
W), including waters of the Susitna, Little Susitna, and Chickaloon 
Rivers below mean higher high water (MHHW). This area provides 
important habitat during ice-free months and is used intensively by 
Cook Inlet beluga between April and November (NMFS 2016a).
    Since 1993, NMFS has conducted annual aerial surveys in June, July 
or August to document the distribution and abundance of beluga whales 
in Cook Inlet. The collective survey results show that beluga whales 
have been consistently found near or in river mouths along the northern 
shores of upper Cook Inlet (i.e., north of East and West Foreland). In 
particular, beluga whale groups are seen in the Susitna River Delta, 
Knik Arm, and along the shores of Chickaloon Bay. Small groups had also 
been recorded seen farther south in Kachemak Bay, Redoubt Bay (Big 
River), and Trading Bay (McArthur River) prior to 1996 but very rarely 
thereafter. Since the mid-1990s, most (96 to 100 percent) beluga whales 
in upper Cook Inlet have been concentrated in shallow areas near river 
mouths, no longer occurring in the central or southern portions of Cook 
Inlet (Hobbs et al. 2008). Based on these aerial surveys, the 
concentration of beluga whales in the northernmost portion of Cook 
Inlet appears to be consistent from June to October (Rugh et al. 2000, 
2004a, 2005, 2006, 2007).
    Though Cook Inlet beluga whales can be found throughout the inlet 
at any time of year, they spend the ice-free months generally in the 
upper Cook Inlet, shifting into the middle and lower Inlet in winter 
(Hobbs et al. 2005). In 1999, one beluga whale was tagged with a 
satellite transmitter, and its movements were recorded from June 
through September of that year. Since 1999, 18 beluga whales in upper 
Cook Inlet have been captured and fitted with satellite tags to provide 
information on their movements during late summer, fall, winter, and 
spring. Using location data from satellite-tagged Cook Inlet belugas, 
Ezer et al. (2013) found most tagged whales were in the lower to middle 
inlet (70 to 100 percent of tagged whales) during January through 
March, near the Susitna River Delta from April to July (60 to 90 
percent of tagged whales) and in the Knik and Turnagain Arms from 
August to December.

[[Page 37464]]

    During the spring and summer, beluga whales are generally 
concentrated near the warmer waters of river mouths where prey 
availability is high and predator occurrence is low (Moore et al. 
2000). Beluga whales in Cook Inlet are believed to mostly calve between 
mid-May and mid-July, and concurrently breed between late spring and 
early summer (NMFS 2016a), primarily in upper Cook Inlet. Movement was 
correlated with the peak discharge of seven major rivers emptying into 
Cook Inlet. Boat-based surveys from 2005 to the present (McGuire and 
Stephens 2017), and initial results from passive acoustic monitoring 
across the entire inlet (Castellote et al. 2016) also support seasonal 
patterns observed with other methods. Other surveys also confirm Cook 
Inlet belugas near the Kenai River during summer months (McGuire and 
Stephens 2017).
    During the summer and fall, beluga whales are concentrated near the 
Susitna River mouth, Knik Arm, Turnagain Arm, and Chickaloon Bay 
(Nemeth et al. 2007) where they feed on migrating eulachon 
(Thaleichthys pacificus) and salmon (Onchorhyncus spp.) (Moore et al. 
2000). Data from tagged whales (14 tags between July and March 2000 
through 2003) show beluga whales use upper Cook Inlet intensively 
between summer and late autumn (Hobbs et al. 2005). Critical Habitat 
Area 1 reflects this summer distribution.
    As late as October, beluga whales tagged with satellite 
transmitters continued to use Knik Arm and Turnagain Arm and Chickaloon 
Bay, but some ranged into lower Cook Inlet south to Chinitna Bay, 
Tuxedni Bay, and Trading Bay (McArthur River) in the fall (Hobbs et al. 
2005). Data from NMFS aerial surveys, opportunistic sighting reports, 
and satellite-tagged beluga whales confirm they are more widely 
dispersed throughout Cook Inlet during the winter months (November-
April), with animals found between Kalgin Island and Point Possession. 
In November, beluga whales moved between Knik Arm, Turnagain Arm, and 
Chickaloon Bay, similar to patterns observed in September (Hobbs et al. 
2005). By December, beluga whales were distributed throughout the upper 
to mid-inlet. From January into March, they moved as far south as 
Kalgin Island and slightly beyond in central offshore waters. Beluga 
whales also made occasional excursions into Knik Arm and Turnagain Arm 
in February and March despite ice cover greater than 90 percent (Hobbs 
et al. 2005).
    During Apache's seismic test program in 2011 along the west coast 
of Redoubt Bay, lower Cook Inlet, a total of 33 beluga whales were 
sighted during the survey (Lomac-MacNair et al. 2013). During Apache's 
2012 seismic program in mid-inlet, a total of 151 sightings of 
approximately 1,463 estimated individual beluga whales were observed 
(Lomac-MacNair et al. 2013). During SAExploration's 2015 seismic 
program, a total of eight sightings of approximately 33 estimated 
individual beluga whales were visually observed during this time period 
and there were two acoustic detections of beluga whales (Kendall et al. 
2015). Hilcorp recently reported 143 sightings of beluga whales May-
August while conducting pipeline work in upper Cook Inlet, which is not 
near the area that seismic surveys are proposed but near some potential 
well sites (Sitkiewicz et al. 2018).
    Ferguson et al. (2015) delineated one ``Small'' and ``Resident'' 
BIA for Cook Inlet beluga whales. Small and Resident BIAs are defined 
as ``areas and time within which small and resident populations occupy 
a limited geographic extent'' (Ferguson et al. 2015). The Cook Inlet 
beluga whale BIA was delineated using the habitat model results of 
Goetz et al. 2012 and the critical habitat boundaries (76 FR 20180).
Harbor Porpoise
    In Alaskan waters, three stocks of harbor porpoises are currently 
recognized for management purposes: Southeast Alaska, Gulf of Alaska, 
and Bering Sea Stocks (Muto et al. 2017). Porpoises found in Cook Inlet 
belong to the Gulf of Alaska Stock which is distributed from Cape 
Suckling to Unimak Pass and most recently was estimated to number 
31,046 individuals (Muto et al. 2017). They are one of the three marine 
mammals (the other two being belugas and harbor seals) regularly seen 
throughout Cook Inlet (Nemeth et al. 2007), especially during spring 
eulachon and summer salmon runs.
    Harbor porpoises primarily frequent the coastal waters of the Gulf 
of Alaska and Southeast Alaska (Dahlheim et al. 2000, 2008), typically 
occurring in waters less than 100 m deep (Hobbs and Waite 2010). The 
range of the Gulf of Alaska stock includes the entire Cook Inlet, 
Shelikof Strait, and the Gulf of Alaska. Harbor porpoises have been 
reported in lower Cook Inlet from Cape Douglas to the West Foreland, 
Kachemak Bay, and offshore (Rugh et al. 2005a). Although they have been 
frequently observed during aerial surveys in Cook Inlet (Shelden et al. 
2014), most sightings are of single animals, and are concentrated at 
Chinitna and Tuxedni bays on the west side of lower Cook Inlet (Rugh et 
al. 2005) and in the upper inlet. The occurrence of larger numbers of 
porpoise in the lower Cook Inlet may be driven by greater availability 
of preferred prey and possibly less competition with beluga whales, as 
belugas move into upper inlet waters to forage on Pacific salmon during 
the summer months (Shelden et al. 2014).
    The harbor porpoise frequently has been observed during summer 
aerial surveys of Cook Inlet, with most sightings of individuals 
concentrated at Chinitna and Tuxedni Bays on the west side of lower 
Cook Inlet (Figure 14 of the application; Rugh et al. 2005). Mating 
probably occurs from June or July to October, with peak calving in May 
and June (as cited in Consiglieri et al. 1982). Small numbers of harbor 
porpoises have been consistently reported in the upper Cook Inlet 
between April and October, except for a recent survey that recorded 
higher numbers than typical. NMFS aerial surveys have identified many 
harbor porpoise sightings throughout Cook Inlet. During Apache's 2012 
seismic program, 137 sightings (190 individuals) were observed between 
May and August (Lomac-MacNair et al. 2013). Lomac-MacNair et al. 2014 
identified 77 groups of harbor porpoise totaling 13 individuals during 
Apache's 2014 seismic survey, both from vessels and aircraft, during 
the month of May. During SAExploration's 2015 seismic survey, 52 
sightings (65 individuals) were observed north of the Forelands 
(Kendall et al. 2015).
    Recent passive acoustic research in Cook Inlet by Alaska Department 
of Fish and Game (ADF&G) and the Marine Mammal Laboratory (MML) have 
indicated that harbor porpoises occur more frequently than expected, 
particularly in the West Foreland area in the spring (Castellote et al. 
2016), although overall numbers are still unknown at this time. Hilcorp 
recently reported 29 sightings of 44 harbor porpoises while conducting 
pipeline work in upper Cook Inlet (Sitkiewicz et al. 2018).
Dall's Porpoise
    Dall's porpoises are widely distributed throughout the North 
Pacific Ocean including preferring deep offshore and shelf-slopes, and 
deep oceanic waters (Muto et al. 2017). The Dall's porpoise range in 
Alaska extends into the southern portion of the Petition region (Figure 
14 of the application). Dall's porpoises are present year-round 
throughout their entire range in the northeast including the Gulf of 
Alaska,

[[Page 37465]]

and occasionally the Cook Inlet area (Morejohn 1979). This porpoise 
also has been observed in lower Cook Inlet, around Kachemak Bay, and 
rarely near Anchor Point (Owl Ridge 2014; BOEM 2015).
    Throughout most of the eastern North Pacific they are present 
during all months of the year, although there may be seasonal onshore-
offshore movements along the west coast of the continental United 
States and winter movements of populations out of areas with ice such 
as Prince William Sound (Muto et al. 2017). Dall's porpoises were 
observed (2 groups, 3 individuals) during Apache's 2014 seismic survey 
which occurred in the summer months (Lomac-MacNair et al. 2014). Dall's 
porpoises were observed during the month of June in 1997 (Iniskin Bay), 
199 (Barren Island), and 2000 (Elizabeth Island, Kamishak Bay and 
Barren Island) (Shelden et al. 2013). Dall's porpoises have been 
observed in lower Cook Inlet, including Kachemak Bay and near Anchor 
Point (Owl Ridge 2014). One Dall's porpoise was observed in August 
north of Nikiski in the middle of the Inlet during SAExploration's 2015 
seismic program (Kendall et al. 2015).
Harbor Seal
    Harbor seals occupy a wide variety of habitats in freshwater and 
saltwater in protected and exposed coastlines and range from Baja 
California north along the west coasts of Washington, Oregon, and 
California, British Columbia, and Southeast Alaska; west through the 
Gulf of Alaska, Prince William Sound, and the Aleutian Islands; and 
north in the Bering Sea to Cape Newenham and the Pribilof Islands. 
Harbor seals are found throughout the entire lower Cook Inlet 
coastline, hauling out on beaches, islands, mudflats, and at the mouths 
of rivers where they whelp and feed (Muto et al. 2017).
    The major haul out sites for harbor seals are located in lower Cook 
Inlet. The presence of harbor seals in upper Cook Inlet is seasonal. In 
Cook Inlet, seal use of western habitats is greater than use of the 
eastern coastline (Boveng et al. 2012). NMFS has documented a strong 
seasonal pattern of more coastal and restricted spatial use during the 
spring and summer for breeding, pupping, and molting, and more wide-
ranging seal movements within and outside of Cook Inlet during the 
winter months (Boveng et al. 2012). Large-scale patterns indicate a 
portion of harbor seals captured in Cook Inlet move out of the area in 
the fall, and into habitats within Shelikof Strait, Northern Kodiak 
Island, and coastal habitats of the Alaska Peninsula, and are most 
concentrated in Kachemak Bay, across Cook Inlet toward Iniskin and 
Iliamna Bays, and south through the Kamishak Bay, Cape Douglas and 
Shelikof Strait regions (Boveng et al. 2012).
    A portion of the Cook Inlet seals move into the Gulf of Alaska and 
Shelikof Strait during the winter months (London et al. 2012). Seals 
move back into Cook Inlet as the breeding season approaches and their 
spatial use is more concentrated around haul-out areas (Boveng et al. 
2012; London et al. 2012). Some seals expand their use of the northern 
portion of Cook Inlet. However, in general, seals that were captured 
and tracked in the southern portion of Cook Inlet remained south of the 
Forelands (Boveng et al. 2012). Important harbor seal haul-out areas 
occur within Kamishak and Kachemak Bays and along the coast of the 
Kodiak Archipelago and the Alaska Peninsula. Chinitna Bay, Clearwater 
and Chinitna Creeks, Tuxedni Bay, Kamishak Bay, Oil Bay, Pomeroy and 
Iniskin Islands, and Augustine Island are also important spring-summer 
breeding and molting areas and known haul-outs sites (Figure 15 of the 
application). Small-scale patterns of movement within Cook Inlet also 
occur (Boveng et al. 2012). Montgomery et al. (2007) recorded over 200 
haul out sites in lower Cook Inlet alone. However, only a few dozen to 
a couple hundred seals seasonally occur in upper Cook Inlet (Rugh et 
al. 2005), mostly at the mouth of the Susitna River where their numbers 
vary in concert with the spring eulachon and summer salmon runs (Nemeth 
et al. 2007; Boveng et al. 2012).
    The Cook Inlet/Shelikof Stock is distributed from Anchorage into 
lower Cook Inlet during summer and from lower Cook Inlet through 
Shelikof Strait to Unimak Pass during winter (Boveng et al. 2012). 
Large numbers concentrate at the river mouths and embayments of lower 
Cook Inlet, including the Fox River mouth in Kachemak Bay, and several 
haul outs have been identified on the southern end of Kalgin Island in 
lower Cook Inlet (Rugh et al. 2005; Boveng et al. 2012). Montgomery et 
al. (2007) recorded over 200 haul-out sites in lower Cook Inlet alone. 
During Apache's 2012 seismic program, harbor seals were observed in the 
project area from early May until the end of the seismic operations in 
late September (Lomac-MacNair et al. 2013). Also in 2012, up to 100 
harbor seals were observed hauled out at the mouths of the Theodore and 
Lewis rivers during monitoring activity associated with Apache's 2012 
Cook Inlet seismic program. During Apache's 2014 seismic program, 492 
groups of harbor seals (613 individuals) were observed. This was the 
highest sighting rate of any marine mammal observed during the summer 
of 2014 (Lomac-MacNair et al. 2014). During SAExploration's 2015 
seismic survey, 823 sightings (1,680 individuals) were observed north 
and between the Forelands (Kendall et al. 2015). Hilcorp recently 
reported 313 sightings of 316 harbor seals while conducting pipeline 
work in upper Cook Inlet (Sitkiewicz et al. 2018).
Steller Sea Lions
    The western DPS (WDPS) stock of Steller sea lions most likely 
occurs in Cook Inlet (78 FR 66139). The center of abundance for the 
Western DPS is considered to extend from Kenai to Kiska Island (NMFS 
2008b). The WDPS of the Steller sea lion is defined as all populations 
west of longitude 144[deg] W to the western end of the Aleutian 
Islands. The range of the WDPS includes 38 rookeries and hundreds of 
haul out sites. The Hilcorp action area only considers the WDPS stock. 
The most recent comprehensive aerial photographic and land-based 
surveys of WDPS Steller sea lions in Alaska were conducted during the 
2014 and 2015 breeding seasons (Fritz et al. 2015).
    The WDPS of Steller sea lions is currently listed as endangered 
under the ESA (55 FR 49204) and designated as depleted under the MMPA. 
Critical habitat was designated on August 27, 1993 (58 FR 45269) south 
of the project area in the Cook Inlet region (Figure 16 of the 
application). The critical habitat designation for the WDPS of Steller 
sea lions was determined to include a 37 km (20 nm) buffer around all 
major haul outs and rookeries, and associated terrestrial, atmospheric, 
and aquatic zones, plus three large offshore foraging areas (Figure 16 
of the application). NMFS also designated no entry zones around 
rookeries (50 CFR 223.202). Designated critical habitat is located 
outside Cook Inlet at Gore Point, Elizabeth Island, Perl Island, and 
Chugach Island (NMFS 2008b).
    The geographic center of Steller sea lion distribution is the 
Aleutian Islands and the Gulf of Alaska, although as the WDPS has 
declined, rookeries in the west became progressively smaller (NMFS 
2008b). Steller sea lion habitat includes terrestrial sites for 
breeding and pupping (rookeries), resting (haul outs), and marine 
foraging areas. Nearly all rookeries are at sites inaccessible to 
terrestrial predators on remote rocks, islands, and reefs. Steller sea 
lions inhabit lower Cook Inlet, especially near Shaw Island and 
Elizabeth Island (Nagahut Rocks) haul out sites (Rugh et al. 2005) but 
are rarely seen in upper

[[Page 37466]]

Cook Inlet (Nemeth et al. 2007). Steller sea lions occur in Cook Inlet 
but south of Anchor Point around the offshore islands and along the 
west coast of the upper inlet in the bays (Chinitna Bay, Iniskin Bay, 
etc.) (Rugh et al. 2005). Portions of the southern reaches of the lower 
inlet are designated as critical habitat, including a 20-nm buffer 
around all major haulout sites and rookeries. Rookeries and haul out 
sites in lower Cook Inlet include those near the mouth of the inlet, 
which are far south of the project area. Steller sea lions feed largely 
on walleye pollock, salmon, and arrowtooth flounder during the summer, 
and walleye pollock and Pacific cod during the winter (Sinclair and 
Zeppelin 2002). Except for salmon, none of these are found in abundance 
in upper Cook Inlet (Nemeth et al. 2007).
    Steller sea lions can travel considerable distances (Baba et al. 
2000). Steller sea lions are not known to migrate annually, but 
individuals may widely disperse outside of the breeding season (late 
May to early July; Jemison et al. 2013; Allen and Angliss 2014). Most 
adult Steller sea lions inhabit rookeries during the breeding season 
(late May to early July). Some juveniles and non-breeding adults occur 
at or near rookeries during the breeding season, but most are on haul 
outs. Adult males may disperse widely after the breeding season and, 
during fall and winter, many sea lions increase use of haul outs, 
especially terrestrial sites but also on sea ice in the Bering Sea 
(NMFS 2008b).
    Steller sea lions have been observed during marine mammal surveys 
conducted in Cook Inlet. In 2012, during Apache's 3D Seismic surveys, 
there were three sightings of approximately four individuals in upper 
Cook Inlet (Lomac-MacNair et al. 2013). Marine mammal observers 
associated with Buccaneer's drilling project off Cape Starichkof 
observed seven Steller sea lions during the summer of 2013 (Owl Ridge 
2014). During SAExploration's 3D Seismic Program in 2015, four Steller 
sea lions were observed in Cook Inlet. One sighting occurred between 
the West and East Forelands, one near Nikiski and one northeast of the 
North Foreland in the center of Cook Inlet (Kendall et al. 2015). 
During NMFS Cook Inlet beluga whale aerial surveys from 2000-2016, 
there were 39 sightings of 769 estimated individual Steller sea lions 
in lower Cook Inlet (Shelden et al. 2017). Sightings of large 
congregations of Steller sea lions during NMFS aerial surveys occurred 
outside the Petition region, on land in the mouth of Cook Inlet (e.g., 
Elizabeth and Shaw Islands). Hilcorp recently reported 1 sighting of 2 
Steller sea lions while conducting pipeline work in upper Cook Inlet 
(Sitkiewicz et al. 2018).
California Sea Lions
    There is limited information on the presence of California sea 
lions in Alaska. From 1973 to 2003, a total of 52 California sea lions 
were reported in Alaska, with sightings increasing in the later years. 
Most sightings occurred in the spring; however, they have been observed 
during all seasons. California sea lion presence in Alaska was 
correlated with increasing population numbers within their southern 
breeding range (Maniscalco et al. 2004).
    There have been relatively few California sea lions observed in 
Alaska, most are often alone or occasionally in small groups of two or 
more and usually associated with Steller sea lions at their haulouts 
and rookeries (Maniscalco et al. 2004). California sea lions are not 
typically observed farther north than southeast Alaska, and sightings 
are very rare in Cook Inlet. California sea lions have not been 
observed during the annual NMFS aerial surveys in Cook Inlet. However, 
a sighting of two California sea lions was documented during for the 
Apache 2012 seismic survey (Lomac-MacNair et al. 2013). Additionally, 
NMFS' anecdotal sighting database has four sightings in Seward and 
Kachemak Bay.
    The California sea lion breeds from the southern Baja Peninsula 
north to A[ntilde]o Nuevo Island, California. Breeding season lasts 
from May to August, and most pups are born from May through July. A UME 
was declared in 2013 for California sea lions in southern California, 
primarily for pups and yearlings. However, the UME does not extend 
through the Pacific Northwest or to Alaska, but California sea lions 
have been included in this rule to cover the unlikely occurrence of 
lone individuals that occur in Cook Inlet every few years. Their 
nonbreeding range extends northward into British Columbia and 
occasionally farther north into Alaskan waters. California sea lions 
have been observed in Alaska during all four seasons; however, most of 
the sightings have occurred during the spring (Maniscalco et al. 2004).
    Sections 3 and 4 of the application summarize available information 
regarding status and trends, distribution and habitat preferences, and 
behavior and life history, of the potentially affected species. 
Additional information regarding population trends and threats may be 
found in NMFS's Stock Assessment Reports (SAR; https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region), and more general information about 
these species (e.g., physical and behavioral descriptions) may be found 
on NMFS' website (https://www.fisheries.noaa.gov/species-directory/).
    All species that could potentially occur in the survey areas are 
included in Table 2. As described below, all 11 species (with 12 
managed stocks) temporally and spatially co-occur with the activity to 
the degree that take is reasonably likely to occur, and we have 
authorizing take of those species.
    In addition, sea otters may be found in Cook Inlet. However, sea 
otters are managed by the U.S. Fish and Wildlife Service and are not 
considered further in this document.

Marine Mammal Hearing

    Hearing is the most important sensory modality for marine mammals 
underwater, and exposure to anthropogenic sound can have deleterious 
effects. To appropriately assess the potential effects of exposure to 
sound, it is necessary to understand the frequency ranges marine 
mammals are able to hear. Current data indicate that not all marine 
mammal species have equal hearing capabilities (e.g., Richardson et 
al., 1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect 
this, Southall et al. (2007) recommended that marine mammals be divided 
into functional hearing groups based on directly measured or estimated 
hearing ranges on the basis of available behavioral response data, 
audiograms derived using auditory evoked potential techniques, 
anatomical modeling, and other data. Note that no direct measurements 
of hearing ability have been successfully completed for mysticetes 
(i.e., low-frequency cetaceans). Subsequently, NMFS (2018) described 
generalized hearing ranges for these marine mammal hearing groups. 
Generalized hearing ranges were chosen based on the approximately 65 dB 
threshold from the normalized composite audiograms, with the exception 
for lower limits for low-frequency cetaceans where the lower bound was 
deemed to be biologically implausible and the lower bound from Southall 
et al. (2007) retained. The functional groups and the associated 
frequencies are indicated below (note that these frequency ranges 
correspond to the range for the composite group, with the entire range 
not necessarily reflecting the capabilities of every species within 
that group):
     Low-frequency cetaceans (mysticetes): Generalized hearing 
is

[[Page 37467]]

estimated to occur between approximately 7 Hz and 35 kHz;
     Mid-frequency cetaceans (larger toothed whales, beaked 
whales, and most delphinids): Generalized hearing is estimated to occur 
between approximately 150 Hz and 160 kHz;
     High-frequency cetaceans (porpoises, river dolphins, and 
members of the genera Kogia and Cephalorhynchus; including two members 
of the genus Lagenorhynchus, on the basis of recent echolocation data 
and genetic data): Generalized hearing is estimated to occur between 
approximately 275 Hz and 160 kHz;
     Pinnipeds in water; Phocidae (true seals): Generalized 
hearing is estimated to occur between approximately 50 Hz to 86 kHz; 
and
     Pinnipeds in water; Otariidae (eared seals): Generalized 
hearing is estimated to occur between 60 Hz and 39 kHz.
    The pinniped functional hearing group was modified from Southall et 
al. (2007) on the basis of data indicating that phocid species have 
consistently demonstrated an extended frequency range of hearing 
compared to otariids, especially in the higher frequency range 
(Hemil[auml] et al., 2006; Kastelein et al., 2009; Reichmuth and Holt, 
2013).
    For more detail concerning these groups and associated frequency 
ranges, please see NMFS (2018) for a review of available information. 
Eleven marine mammal species (eight cetacean and three pinniped (two 
otariid and one phocid) species) have the reasonable potential to co-
occur with the survey activities. Please refer to Table 2. Of the 
cetacean species that may be present, four are classified as low-
frequency cetaceans (i.e., all mysticete species), two are classified 
as mid-frequency cetaceans (i.e., all delphinid and ziphiid species and 
the sperm whale), and two are classified as high-frequency cetaceans 
(i.e., harbor porpoise and Kogia spp.).

Potential Effects of Specified Activities on Marine Mammals and Their 
Habitat

    This section includes a summary and discussion of the ways that 
components of the specified activity may impact marine mammals and 
their habitat. The Estimated Take by Incidental Harassment section 
later in this document includes a quantitative analysis of the number 
of individuals that are expected to be taken by this activity. The 
Negligible Impact Analysis and Determination section considers the 
content of this section, the Estimated Take by Incidental Harassment 
section, and the Mitigation section, to draw conclusions regarding the 
likely impacts of these activities on the reproductive success or 
survivorship of individuals and how those impacts on individuals are 
likely to impact marine mammal species or stocks.
Description of Active Acoustic Sound Sources
    This section contains a brief technical background on sound, the 
characteristics of certain sound types, and on metrics used in this 
rule in as much as the information is relevant to the specified 
activity and to a discussion of the potential effects of the specified 
activity on marine mammals found later in this document.
    Sound travels in waves, the basic components of which are 
frequency, wavelength, velocity, and amplitude. Frequency is the number 
of pressure waves that pass by a reference point per unit of time and 
is measured in Hz or cycles per second. Wavelength is the distance 
between two peaks or corresponding points of a sound wave (length of 
one cycle). Higher frequency sounds have shorter wavelengths than lower 
frequency sounds, and typically attenuate (decrease) more rapidly, 
except in certain cases in shallower water. Amplitude is the height of 
the sound pressure wave or the ``loudness'' of a sound and is typically 
described using the relative unit of the dB. A sound pressure level 
(SPL) in dB is described as the ratio between a measured pressure and a 
reference pressure (for underwater sound, this is 1 microPascal 
([mu]Pa)) and is a logarithmic unit that accounts for large variations 
in amplitude; therefore, a relatively small change in dB corresponds to 
large changes in sound pressure. The source level (SL) represents the 
SPL referenced at a distance of 1 m from the source (referenced to 1 
[mu]Pa) while the received level is the SPL at the listener's position 
(referenced to 1 [mu]Pa).
    Root mean square (rms) is the quadratic mean sound pressure over 
the duration of an impulse. Root mean square is calculated by squaring 
all of the sound amplitudes, averaging the squares, and then taking the 
square root of the average (Urick, 1983). Root mean square accounts for 
both positive and negative values; squaring the pressures makes all 
values positive so that they may be accounted for in the summation of 
pressure levels (Hastings and Popper, 2005). This measurement is often 
used in the context of discussing behavioral effects, in part because 
behavioral effects, which often result from auditory cues, may be 
better expressed through averaged units than by peak pressures.
    Sound exposure level (SEL; represented as dB re 1 [mu]Pa2-s) 
represents the total energy contained within a pulse and considers both 
intensity and duration of exposure. Peak sound pressure (also referred 
to as zero-to-peak sound pressure or 0-p) 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. 
Another common metric is peak-to-peak sound pressure (pk-pk), which is 
the algebraic difference between the peak positive and peak negative 
sound pressures. Peak-to-peak pressure is typically approximately 6 dB 
higher than peak pressure (Southall et al., 2007).
    When underwater objects vibrate or activity occurs, sound-pressure 
waves are created. These waves alternately compress and decompress the 
water as the sound wave travels. Underwater sound waves radiate in a 
manner similar to ripples on the surface of a pond and may be either 
directed in a beam or beams or may radiate in all directions 
(omnidirectional sources), as is the case for pulses produced by the 
airgun arrays considered here. The compressions and decompressions 
associated with sound waves are detected as changes in pressure by 
aquatic life and man-made sound receptors such as hydrophones.
    Even in the absence of sound from the specified activity, the 
underwater environment is typically loud due to ambient sound. Ambient 
sound is defined as environmental background sound levels lacking a 
single source or point (Richardson et al., 1995), and the sound level 
of a region is defined by the total acoustical energy being generated 
by known and unknown sources. These sources may include physical (e.g., 
wind and waves, earthquakes, ice, atmospheric sound), biological (e.g., 
sounds produced by marine mammals, fish, and invertebrates), and 
anthropogenic (e.g., vessels, dredging, construction) sound. A number 
of sources contribute to ambient sound, including the following 
(Richardson et al., 1995):
     Wind and waves: The complex interactions between wind and 
water surface, including processes such as breaking waves and wave-
induced bubble oscillations and cavitation, are a main source of 
naturally occurring ambient sound for frequencies between 200 Hz and 50 
kilohertz (kHz) (Mitson, 1995). In general, ambient sound levels tend 
to increase with increasing wind speed and wave height. Surf sound 
becomes important near shore, with measurements collected at a distance 
of 8.5 km from shore showing an increase of 10 dB in the 100 to 700 Hz 
band during heavy surf conditions;

[[Page 37468]]

     Precipitation: Sound from rain and hail impacting the 
water surface can become an important component of total sound at 
frequencies above 500 Hz, and possibly down to 100 Hz during quiet 
times;
     Biological: Marine mammals can contribute significantly to 
ambient sound levels, as can some fish and snapping shrimp. The 
frequency band for biological contributions is from approximately 12 Hz 
to over 100 kHz; and
     Anthropogenic: Sources of ambient sound related to human 
activity include transportation (surface vessels), dredging and 
construction, oil and gas drilling and production, seismic surveys, 
sonar, explosions, and ocean acoustic studies. Vessel noise typically 
dominates the total ambient sound for frequencies between 20 and 300 
Hz. In general, the frequencies of anthropogenic sounds are below 1 kHz 
and, if higher frequency sound levels are created, they attenuate 
rapidly. Sound from identifiable anthropogenic sources other than the 
activity of interest (e.g., a passing vessel) is sometimes termed 
background sound, as opposed to ambient sound.
    The sum of the various natural and anthropogenic sound sources at 
any given location and time--which comprise ``ambient'' or 
``background'' sound--depends not only on the source levels (as 
determined by current weather conditions and levels of biological and 
human activity) but also on the ability of sound to propagate through 
the environment. In turn, sound propagation is dependent on the 
spatially and temporally varying properties of the water column and sea 
floor and is frequency-dependent. As a result of the dependence on a 
large number of varying factors, ambient sound levels can be expected 
to vary widely over both coarse and fine spatial and temporal scales. 
Sound levels at a given frequency and location can vary by 10-20 dB 
from day to day (Richardson et al., 1995). The result is that, 
depending on the source type and its intensity, sound from a given 
activity may be a negligible addition to the local environment or could 
form a distinctive signal that may affect marine mammals. Details of 
source types are described in the following text.
    Sounds are often considered to fall into one of two general types: 
Pulsed and non-pulsed (defined in the following). The distinction 
between these two sound types is important because they have differing 
potential to cause physical effects, particularly with regard to 
hearing (e.g., Ward, 1997 in Southall et al., 2007). Please see 
Southall et al. (2007) for an in-depth discussion of these concepts.
    Pulsed sound sources (e.g., airguns, explosions, gunshots, sonic 
booms, impact pile driving) produce signals that are brief (typically 
considered to be less than one second), broadband, atonal transients 
(ANSI, 1986, 2005; Harris, 1998; NIOSH, 1998; ISO, 2003) and occur 
either as isolated events or repeated in some succession. Pulsed sounds 
are all characterized by a relatively rapid rise from ambient pressure 
to a maximal pressure value followed by a rapid decay period that may 
include a period of diminishing, oscillating maximal and minimal 
pressures and generally have an increased capacity to induce physical 
injury as compared with sounds that lack these features.
    Non-pulsed sounds can be tonal, narrowband, or broadband, brief or 
prolonged, and may be either continuous or non-continuous (ANSI, 1995; 
NIOSH, 1998). Some of these non-pulsed sounds can be transient signals 
of short duration but without the essential properties of pulses (e.g., 
rapid rise time). Examples of non-pulsed sounds include those produced 
by vessels, aircraft, machinery operations such as drilling or 
dredging, vibratory pile driving, and active sonar systems (such as 
those used by the U.S. Navy). The duration of such sounds, as received 
at a distance, can be greatly extended in a highly reverberant 
environment.
    Airgun arrays produce pulsed signals with energy in a frequency 
range from about 10-2,000 Hz, with most energy radiated at frequencies 
below 200 Hz. The amplitude of the acoustic wave emitted from the 
source is equal in all directions (i.e., omnidirectional), but airgun 
arrays do possess some directionality due to different phase delays 
between guns in different directions. Airgun arrays are typically tuned 
to maximize functionality for data acquisition purposes, meaning that 
sound transmitted in horizontal directions and at higher frequencies is 
minimized to the extent possible.
    As described above, two types of sub-bottom profiler will also be 
used by Hilcorp during the geotechnical and geohazard surveys: A low 
resolution unit (1-4 kHz) and a high resolution unit (2-24 kHz).
    Potential Effects of Underwater Sound--Please refer to the 
information given previously (``Description of Active Acoustic Sound 
Sources'') regarding sound, characteristics of sound types, and metrics 
used in this document. Note that, in the following discussion, we refer 
in many cases to a recent review article concerning studies of noise-
induced hearing loss conducted from 1996-2015 (i.e., Finneran, 2015). 
For study-specific citations, please see that work. Anthropogenic 
sounds cover a broad range of frequencies and sound levels and can have 
a range of highly variable impacts on marine life, from none or minor 
to potentially severe responses, depending on received levels, duration 
of exposure, behavioral context, and various other factors. The 
potential effects of underwater sound from active acoustic sources can 
potentially result in one or more of the following: Temporary or 
permanent hearing impairment, non-auditory physical or physiological 
effects, behavioral disturbance, stress, and masking (Richardson et 
al., 1995; Gordon et al., 2004; Nowacek et al., 2007; Southall et al., 
2007; G[ouml]tz et al., 2009). The degree of effect is intrinsically 
related to the signal characteristics, received level, distance from 
the source, and duration of the sound exposure. In general, sudden, 
high level sounds can cause hearing loss, as can longer exposures to 
lower level sounds. Temporary or permanent loss of hearing will occur 
almost exclusively for noise within an animal's hearing range. We first 
describe specific manifestations of acoustic effects before providing 
discussion specific to the use of airguns.
    Richardson et al. (1995) described zones of increasing intensity of 
effect that might be expected to occur, in relation to distance from a 
source and assuming that the signal is within an animal's hearing 
range. First is the area within which the acoustic signal would be 
audible (potentially perceived) to the animal but not strong enough to 
elicit any overt behavioral or physiological response. The next zone 
corresponds with the area where the signal is audible to the animal and 
of sufficient intensity to elicit behavioral or physiological 
responsiveness. Third is a zone within which, for signals of high 
intensity, the received level is sufficient to potentially cause 
discomfort or tissue damage to auditory or other systems. Overlaying 
these zones to a certain extent is the area within which masking (i.e., 
when a sound interferes with or masks the ability of an animal to 
detect a signal of interest that is above the absolute hearing 
threshold) may occur; the masking zone may be highly variable in size.
    We describe the more severe effects certain non-auditory physical 
or physiological effects only briefly as we do not expect that use of 
airgun arrays, sub-bottom profilers, drill rig construction, or sheet 
pile driving are

[[Page 37469]]

reasonably likely to result in such effects (see below for further 
discussion). Potential effects from impulsive sound sources can range 
in severity from effects such as behavioral disturbance or tactile 
perception to physical discomfort, slight injury of the internal organs 
and the auditory system, or mortality (Yelverton et al., 1973). Non-
auditory physiological effects or injuries that theoretically might 
occur in marine mammals exposed to high level underwater sound or as a 
secondary effect of extreme behavioral reactions (e.g., change in dive 
profile as a result of an avoidance reaction) caused by exposure to 
sound include neurological effects, bubble formation, resonance 
effects, and other types of organ or tissue damage (Cox et al., 2006; 
Southall et al., 2007; Zimmer and Tyack, 2007; Tal et al., 2015). The 
suite of activities considered here do not involve the use of devices 
such as explosives or mid-frequency tactical sonar that are associated 
with these types of effects.
    1. Threshold Shift--Marine mammals exposed to high-intensity sound, 
or to lower-intensity sound for prolonged periods, can experience 
hearing threshold shift (TS), which is the loss of hearing sensitivity 
at certain frequency ranges (Finneran, 2015). TS can be permanent 
(PTS), in which case the loss of hearing sensitivity is not fully 
recoverable, or temporary (TTS), in which case the animal's hearing 
threshold would recover over time (Southall et al., 2007). Repeated 
sound exposure that leads to TTS could cause PTS. In severe cases of 
PTS, there can be total or partial deafness, while in most cases the 
animal has an impaired ability to hear sounds in specific frequency 
ranges (Kryter, 1985).
    When PTS occurs, there is physical damage to the sound receptors in 
the ear (i.e., tissue damage), whereas TTS represents primarily tissue 
fatigue and is reversible (Southall et al., 2007). In addition, other 
investigators have suggested that TTS is within the normal bounds of 
physiological variability and tolerance and does not represent physical 
injury (e.g., Ward, 1997). Therefore, NMFS does not consider TTS to 
constitute auditory injury.
    Relationships between TTS and PTS thresholds have not been studied 
in marine mammals. There is no PTS data for cetaceans, but such 
relationships are assumed to be similar to those in humans and other 
terrestrial mammals. PTS typically occurs at exposure levels at least 
several decibels above (a 40-dB threshold shift approximates PTS onset; 
e.g., Kryter et al., 1966; Miller, 1974) which would induce mild TTS (a 
6-dB threshold shift approximates TTS onset; e.g., Southall et al., 
2007). Based on data from terrestrial mammals, a precautionary 
assumption is that the PTS thresholds for impulse sounds (such as 
airgun pulses as received close to the source) are at least 6 dB higher 
than the TTS threshold on a peak-pressure basis, and PTS cumulative 
sound exposure level (SELcum) thresholds are 15 to 20 dB higher than 
TTS SELcum thresholds (Southall et al., 2007). Given the higher level 
of sound combined with longer exposure duration necessary to cause PTS, 
it is expected that limited PTS could occur from the activities. For 
mid-frequency cetaceans in particular, potential protective mechanisms 
may help limit onset of TTS or prevent onset of PTS. Such mechanisms 
include dampening of hearing, auditory adaptation, or behavioral 
amelioration (e.g., Nachtigall and Supin, 2013; Miller et al., 2012; 
Finneran et al., 2015; Popov et al., 2016). Given the higher level of 
sound, longer durations of exposure necessary to cause PTS, it is 
possible but unlikely PTS would occur during the seismic surveys, 
geotechnical surveys, or other exploratory drilling activities.
    TTS is the mildest form of hearing impairment that can occur during 
exposure to sound (Kryter, 1985). While experiencing TTS, the hearing 
threshold rises, and a sound must be at a higher level in order to be 
heard. In terrestrial and marine mammals, TTS can last from minutes or 
hours to days (in cases of strong TTS). In many cases, hearing 
sensitivity recovers rapidly after exposure to the sound ends. Few data 
on sound levels and durations necessary to elicit mild TTS have been 
obtained for marine mammals.
    Marine mammal hearing plays a critical role in communication with 
conspecifics, and interpretation of environmental cues for purposes 
such as predator avoidance and prey capture. Depending on the degree 
(elevation of threshold in dB), duration (i.e., recovery time), and 
frequency range of TTS, and the context in which it is experienced, TTS 
can have effects on marine mammals ranging from discountable to 
serious. For example, a marine mammal may be able to readily compensate 
for a brief, relatively small amount of TTS in a non-critical frequency 
range that occurs during a time where ambient noise is lower and there 
are not as many competing sounds present. Alternatively, a larger 
amount and longer duration of TTS sustained during time when 
communication is critical for successful mother/calf interactions could 
have more serious impacts.
    Finneran et al. (2015) measured hearing thresholds in three captive 
bottlenose dolphins before and after exposure to ten pulses produced by 
a seismic airgun in order to study TTS induced after exposure to 
multiple pulses. Exposures began at relatively low levels and gradually 
increased over a period of several months, with the highest exposures 
at peak SPLs from 196 to 210 dB and cumulative (unweighted) SELs from 
193-195 dB. No substantial TTS was observed. In addition, behavioral 
reactions were observed that indicated that animals can learn behaviors 
that effectively mitigate noise exposures (although exposure patterns 
must be learned, which is less likely in wild animals than for the 
captive animals considered in this study). The authors note that the 
failure to induce more significant auditory effects is likely due to 
the intermittent nature of exposure, the relatively low peak pressure 
produced by the acoustic source, and the low-frequency energy in airgun 
pulses as compared with the frequency range of best sensitivity for 
dolphins and other mid-frequency cetaceans.
    Currently, TTS data only exist for four species of cetaceans 
(bottlenose dolphin (Tursiops truncatus), beluga whale (Delphinapterus 
leucas), harbor porpoise, and Yangtze finless porpoise (Neophocoena 
asiaeorientalis)) and five species of pinnipeds (northern elephant 
seal, harbor seal, and California sea lion) exposed to a limited number 
of sound sources (i.e., mostly tones and octave-band noise) in 
laboratory settings (Finneran, 2015). TTS was not observed in trained 
spotted (Phoca largha) and ringed (Pusa hispida) seals exposed to 
impulsive noise at levels matching previous predictions of TTS onset 
(Reichmuth et al., 2016). In general, harbor seals and harbor porpoises 
have a lower TTS onset than other measured pinniped or cetacean species 
(Finneran, 2015). Additionally, the existing marine mammal TTS data 
come from a limited number of individuals within these species. There 
are no data available on noise-induced hearing loss for mysticetes. For 
summaries of data on TTS in marine mammals or for further discussion of 
TTS onset thresholds, please see Southall et al. (2007), Finneran and 
Jenkins (2012), Finneran (2015), and Table 5 in NMFS (2018).
    Critical questions remain regarding the rate of TTS growth and 
recovery after exposure to intermittent noise and the effects of single 
and multiple pulses. Data at present are also insufficient to construct 
generalized models for recovery and determine the time necessary to 
treat subsequent exposures as independent events. More information is 
needed on the

[[Page 37470]]

relationship between auditory evoked potential and behavioral measures 
of TTS for various stimuli. For summaries of data on TTS in marine 
mammals or for further discussion of TTS onset thresholds, please see 
Southall et al. (2007), Finneran and Jenkins (2012), Finneran (2015), 
and NMFS (2016).
    Marine mammals in the action area during the activities are less 
likely to incur TTS hearing impairment from some of the sources to be 
used due to the characteristics of the sound sources, particularly 
sources such as the water jets, which include lower source levels (176 
dB @1m) and generally very short pulses and duration of the sound. Even 
for high-frequency cetacean species (e.g., harbor porpoises), which may 
have increased sensitivity to TTS (Lucke et al., 2009; Kastelein et 
al., 2012b), individuals would have to make a very close approach and 
also remain very close to vessels operating these sources in order to 
receive multiple exposures at relatively high levels, as would be 
necessary to cause TTS. Intermittent exposures--as would occur due to 
the brief, transient signals produced by these sources--require a 
higher cumulative SEL to induce TTS than would continuous exposures of 
the same duration (i.e., intermittent exposure results in lower levels 
of TTS) (Mooney et al., 2009a; Finneran et al., 2010).
    Moreover, most marine mammals would more likely avoid a loud sound 
source rather than swim in such close proximity as to result in TTS 
(much less PTS). Kremser et al. (2005) noted that the probability of a 
cetacean swimming through the area of exposure when a sub-bottom 
profiler emits a pulse is small--because if the animal was in the area, 
it would have to pass the transducer at close range in order to be 
subjected to sound levels that could cause temporary threshold shift 
and will likely exhibit avoidance behavior to the area near the 
transducer rather than swim through at such a close range. Further, the 
restricted beam shape of the sub-bottom profiler and other geophysical 
survey equipment makes it unlikely that an animal would be exposed more 
than briefly during the passage of the vessel. Boebel et al. (2005) 
concluded similarly for single and multibeam echosounders, and more 
recently, Lurton (2016) conducted a modeling exercise and concluded 
similarly that likely potential for acoustic injury from these types of 
systems is negligible, but that behavioral response cannot be ruled 
out. Animals may avoid the area around the survey vessels, thereby 
reducing exposure. Effects of non-pulsed sound on marine mammals, such 
as vibratory pile driving, are less studied. In a study by Malme et al. 
(1986) on gray whales as well as Richardson et al. (1997) on beluga 
whales, the only reactions documented in response to drilling sound 
playbacks were behavioral reactions. Any disturbance to marine mammals 
is likely to be in the form of temporary avoidance or alteration of 
opportunistic foraging behavior near the survey location.
    2. Behavioral Effects--Behavioral disturbance may include a variety 
of effects, including subtle changes in behavior (e.g., minor or brief 
avoidance of an area or changes in vocalizations), more conspicuous 
changes in similar behavioral activities, and more sustained and/or 
potentially severe reactions, such as displacement from or abandonment 
of high-quality habitat. Behavioral responses to sound are highly 
variable and context-specific and any reactions depend on numerous 
intrinsic and extrinsic factors (e.g., species, state of maturity, 
experience, current activity, reproductive state, auditory sensitivity, 
time of day), as well as the interplay between factors (e.g., 
Richardson et al., 1995; Wartzok et al., 2003; Southall et al., 2007; 
Weilgart, 2007; Archer et al., 2010). Behavioral reactions can vary not 
only among individuals but also within an individual, depending on 
previous experience with a sound source, context, and numerous other 
factors (Ellison et al., 2012), and can vary depending on 
characteristics associated with the sound source (e.g., whether it is 
moving or stationary, number of sources, distance from the source). 
Please see Appendices B-C of Southall et al. (2007) for a review of 
studies involving marine mammal behavioral responses to sound.
    Habituation can occur when an animal's response to a stimulus wanes 
with repeated exposure, usually in the absence of unpleasant associated 
events (Wartzok et al., 2003). Animals are most likely to habituate to 
sounds that are predictable and unvarying. It is important to note that 
habituation is appropriately considered as a ``progressive reduction in 
response to stimuli that are perceived as neither aversive nor 
beneficial,'' rather than as, more generally, moderation in response to 
human disturbance (Bejder et al., 2009). The opposite process is 
sensitization, when an unpleasant experience leads to subsequent 
responses, often in the form of avoidance, at a lower level of 
exposure. As noted, behavioral state may affect the type of response. 
For example, animals that are resting may show greater behavioral 
change in response to disturbing sound levels than animals that are 
highly motivated to remain in an area for feeding (Richardson et al., 
1995; NRC, 2003; Wartzok et al., 2003). Controlled experiments with 
captive marine mammals have showed pronounced behavioral reactions, 
including avoidance of loud sound sources (Ridgway et al., 1997). 
Observed responses of wild marine mammals to loud pulsed sound sources 
(typically seismic airguns or acoustic harassment devices) have been 
varied but often consist of avoidance behavior or other behavioral 
changes suggesting discomfort (Morton and Symonds, 2002; see also 
Richardson et al., 1995; Nowacek et al., 2007). However, many 
delphinids approach acoustic source vessels with no apparent discomfort 
or obvious behavioral change (e.g., Barkaszi et al., 2012).
    Available studies show wide variation in response to underwater 
sound; therefore, it is difficult to predict specifically how any given 
sound in a particular instance might affect marine mammals perceiving 
the signal. If a marine mammal does react briefly to an underwater 
sound by changing its behavior or moving a small distance, the impacts 
of the change are unlikely to be significant to the individual, let 
alone the stock or population. However, if a sound source displaces 
marine mammals from an important feeding or breeding area for a 
prolonged period, impacts on individuals and populations could be 
significant (e.g., Lusseau and Bejder, 2007; Weilgart, 2007; NRC, 
2005). However, there are broad categories of potential response, which 
we describe in greater detail here, that include alteration of dive 
behavior, alteration of foraging behavior, effects to breathing, 
interference with or alteration of vocalization, avoidance, and flight.
    Changes in dive behavior can vary widely, and may consist of 
increased or decreased dive times and surface intervals as well as 
changes in the rates of ascent and descent during a dive (e.g., Frankel 
and Clark 2000; Ng and Leung 2003; Nowacek et al. 2004; Goldbogen et 
al. 2013). Variations in dive behavior may reflect interruptions in 
biologically significant activities (e.g., foraging) or they may be of 
little biological significance. The impact of an alteration to dive 
behavior resulting from an acoustic exposure depends on what the animal 
is doing at the time of the exposure and the type and magnitude of the 
response.
    Disruption of feeding behavior can be difficult to correlate with 
anthropogenic sound exposure, so it is usually inferred by observed 
displacement from known

[[Page 37471]]

foraging areas, the appearance of secondary indicators (e.g., bubble 
nets or sediment plumes), or changes in dive behavior. As for other 
types of behavioral response, the frequency, duration, and temporal 
pattern of signal presentation, as well as differences in species 
sensitivity, are likely contributing factors to differences in response 
in any given circumstance (e.g., Croll et al. 2001; Nowacek et al. 
2004; Madsen et al. 2006; Yazvenko et al. 2007). A determination of 
whether foraging disruptions incur fitness consequences requires 
information on or estimates of the energetic requirements of the 
affected individuals and the relationship between prey availability, 
foraging effort and success, and the life history stage of the animal.
    Visual tracking, passive acoustic monitoring, and movement 
recording tags were used to quantify sperm whale behavior prior to, 
during, and following exposure to airgun arrays at received levels in 
the range 140-160 dB at distances of 7-13 km, following a phase-in of 
sound intensity and full array exposures at 1-13 km (Madsen et al., 
2006; Miller et al., 2009). Sperm whales did not exhibit horizontal 
avoidance behavior at the surface. However, foraging behavior may have 
been affected. The sperm whales exhibited 19 percent less vocal (buzz) 
rate during full exposure relative to post exposure, and the whale that 
was approached most closely had an extended resting period and did not 
resume foraging until the airguns had ceased firing. The remaining 
whales continued to execute foraging dives throughout exposure; 
however, swimming movements during foraging dives were six percent 
lower during exposure than control periods (Miller et al., 2009). These 
data raise concerns that seismic surveys may impact foraging behavior 
in sperm whales, although more data are required to understand whether 
the differences were due to exposure or natural variation in sperm 
whale behavior (Miller et al., 2009). Variations in respiration 
naturally vary with different behaviors and alterations to breathing 
rate as a function of acoustic exposure can be expected to co-occur 
with other behavioral reactions, such as a flight response or an 
alteration in diving. However, respiration rates in and of themselves 
may be representative of annoyance or an acute stress response. Various 
studies have shown that respiration rates may either be unaffected or 
could increase, depending on the species and signal characteristics, 
again highlighting the importance in understanding species differences 
in the tolerance of underwater noise when determining the potential for 
impacts resulting from anthropogenic sound exposure (e.g., Kastelein et 
al., 2001, 2005, 2006; Gailey et al., 2007).
    Marine mammals vocalize for different purposes and across multiple 
modes, such as whistling, echolocation click production, calling, and 
singing. Changes in vocalization behavior in response to anthropogenic 
noise can occur for any of these modes and may result from a need to 
compete with an increase in background noise or may reflect increased 
vigilance or a startle response. For example, in the presence of 
potentially masking signals, humpback whales and killer whales have 
been observed to increase the length of their songs (Miller et al., 
2000; Fristrup et al., 2003; Foote et al., 2004), while right whales 
have been observed to shift the frequency content of their calls upward 
while reducing the rate of calling in areas of increased anthropogenic 
noise (Parks et al., 2007). In some cases, animals may cease sound 
production during production of aversive signals (Bowles et al., 1994).
    Cerchio et al. (2014) used passive acoustic monitoring to document 
the presence of singing humpback whales off the coast of northern 
Angola and to opportunistically test for the effect of seismic survey 
activity on the number of singing whales. Two recording units were 
deployed between March and December 2008 in the offshore environment, 
and the numbers of singers were counted every hour. Generalized 
Additive Mixed Models were used to assess the effect of survey day 
(seasonality), hour (diel variation), moon phase, and received levels 
of noise (measured from a single pulse during each ten minute sampled 
period) on singer number. The number of singers significantly decreased 
with increasing received level of noise, suggesting that humpback whale 
breeding activity was disrupted to some extent by the survey activity.
    Castellote et al. (2012) reported acoustic and behavioral changes 
by fin whales in response to shipping and airgun noise. Acoustic 
features of fin whale song notes recorded in the Mediterranean Sea and 
northeast Atlantic Ocean were compared for areas with different 
shipping noise levels and traffic intensities and during a seismic 
airgun survey. During the first 72 hours of the survey, a steady 
decrease in song received levels and bearings to singers indicated that 
whales moved away from the acoustic source and out of the study area. 
This displacement persisted for a time period well beyond the 10-day 
duration of seismic airgun activity, providing evidence that fin whales 
may avoid an area for an extended period in the presence of increased 
noise. The authors hypothesize that fin whale acoustic communication is 
modified to compensate for increased background noise and that a 
sensitization process may play a role in the observed temporary 
displacement.
    Seismic pulses at average received levels of 131 dB re 1 
[micro]Pa2-s caused blue whales to increase call production (Di Iorio 
and Clark, 2010). In contrast, McDonald et al. (1995) tracked a blue 
whale with seafloor seismometers and reported that it stopped 
vocalizing and changed its travel direction at a range of 10 km from 
the acoustic source vessel (estimated received level 143 dB pk-pk). 
Blackwell et al. (2013) found that bowhead whale call rates dropped 
significantly at onset of airgun use at sites with a median distance of 
41-45 km from the survey. Blackwell et al. (2015) expanded this 
analysis to show that whales actually increased calling rates as soon 
as airgun signals were detectable before ultimately decreasing calling 
rates at higher received levels (i.e., 10-minute SELcum of ~127 dB). 
Overall, these results suggest that bowhead whales may adjust their 
vocal output in an effort to compensate for noise before ceasing 
vocalization effort and ultimately deflecting from the acoustic source 
(Blackwell et al., 2013, 2015). These studies demonstrate that even low 
levels of noise received far from the source can induce changes in 
vocalization and/or behavior for mysticetes.
    Avoidance is the displacement of an individual from an area or 
migration path as a result of the presence of a sound or other 
stressors, and is one of the most obvious manifestations of disturbance 
in marine mammals (Richardson et al., 1995). For example, gray whales 
are known to change direction--deflecting from customary migratory 
paths--in order to avoid noise from seismic surveys (Malme et al., 
1984). Humpback whales showed avoidance behavior in the presence of an 
active seismic array during observational studies and controlled 
exposure experiments in western Australia (McCauley et al., 2000). 
Avoidance may be short-term, with animals returning to the area once 
the noise has ceased (e.g., Bowles et al., 1994; Stone et al., 2000; 
Morton and Symonds, 2002; Gailey et al., 2007). Longer-term 
displacement is possible, however, which may lead to changes in 
abundance or distribution patterns of the affected species in the 
affected region if habituation to the presence of

[[Page 37472]]

the sound does not occur (e.g., Bejder et al., 2006; Teilmann et al., 
2006).
    A flight response is a dramatic change in normal movement to a 
directed and rapid movement away from the perceived location of a sound 
source. The flight response differs from other avoidance responses in 
the intensity of the response (e.g., directed movement, rate of 
travel). Relatively little information on flight responses of marine 
mammals to anthropogenic signals exist, although observations of flight 
responses to the presence of predators have occurred (Connor and 
Heithaus, 1996). The result of a flight response could range from 
brief, temporary exertion and displacement from the area where the 
signal provokes flight to, in extreme cases, marine mammal strandings 
(Evans and England, 2001). However, it should be noted that response to 
a perceived predator does not necessarily invoke flight (Ford and 
Reeves, 2008), and whether individuals are solitary or in groups may 
influence the response.
    Behavioral disturbance can also impact marine mammals in more 
subtle ways. Increased vigilance may result in costs related to 
diversion of focus and attention (i.e., when a response consists of 
increased vigilance, it may come at the cost of decreased attention to 
other critical behaviors such as foraging or resting). These effects 
have generally not been demonstrated for marine mammals, but studies 
involving fish and terrestrial animals have shown that increased 
vigilance may substantially reduce feeding rates (e.g., Beauchamp and 
Livoreil 1997; Purser and Radford 2011). In addition, chronic 
disturbance can cause population declines through reduction of fitness 
(e.g., decline in body condition) and subsequent reduction in 
reproductive success, survival, or both (e.g., Harrington and Veitch 
1992; Daan et al. 1996; Bradshaw et al. 1998). However, Ridgway et al. 
(2006) reported that increased vigilance in bottlenose dolphins exposed 
to sound over a five-day period did not cause any sleep deprivation or 
stress effects.
    Many animals perform vital functions, such as feeding, resting, 
traveling, and socializing, on a diel cycle (24-hour cycle). Disruption 
of such functions resulting from reactions to stressors such as sound 
exposure are more likely to be significant if they last more than one 
diel cycle or recur on subsequent days (Southall et al., 2007). 
Consequently, a behavioral response lasting less than one day and not 
recurring on subsequent days is not considered particularly severe 
unless it could directly affect reproduction or survival (Southall et 
al., 2007). Note that there is a difference between multi-day 
substantive behavioral reactions and multi-day anthropogenic 
activities. For example, just because an activity lasts for multiple 
days does not necessarily mean that individual animals are either 
exposed to activity-related stressors for multiple days or, further, 
exposed in a manner resulting in sustained multi-day substantive 
behavioral responses.
    Stone (2015) reported data from at-sea observations during 1,196 
seismic surveys from 1994 to 2010. When large arrays of airguns 
(considered to be 500 in\3\ or more) were firing, lateral displacement, 
more localized avoidance, or other changes in behavior were evident for 
most odontocetes. However, significant responses to large arrays were 
found only for the minke whale and fin whale. Behavioral responses 
observed included changes in swimming or surfacing behavior, with 
indications that cetaceans remained near the water surface at these 
times. Cetaceans were recorded as feeding less often when large arrays 
were active. Behavioral observations of gray whales during a seismic 
survey monitored whale movements and respirations pre-, during and 
post-seismic survey (Gailey et al., 2016). Behavioral state and water 
depth were the best `natural' predictors of whale movements and 
respiration and, after considering natural variation, none of the 
response variables were significantly associated with seismic survey or 
vessel sounds.
    Marine mammals are likely to avoid the activities, especially 
harbor porpoises, while the harbor seals might be attracted to them out 
of curiosity. However, because the sub-bottom profilers and seismic 
equipment operate from moving vessels, the area (relative to the 
available habitat in Cook Inlet) and time that this equipment will be 
affecting a given location is very small. Further, for mobile sources, 
once an area has been surveyed, it is not likely that it will be 
surveyed again, therefore reducing the likelihood of repeated 
geophysical and geotechnical survey impacts within the survey area. The 
isopleths for harassment for the stationary sources considered in this 
document are small relative to those for mobile sources. Therefore, 
while the sound is concentrated in the same area for the duration of 
the activity (duration of pile driving, VSP, etc), the amount of area 
affected by noise levels which we expect may cause harassment are small 
relative to the mobile sources. Additionally, animals may more 
predictably avoid the area of the disturbance as the source is 
stationary. Overall duration of these sound sources is still short and 
unlikely to cause more than temporary disturbance.
    We have also considered the potential for severe behavioral 
responses such as stranding and associated indirect injury or mortality 
from Hilcorp's use of high resolution geophysical survey equipment, on 
the basis of a 2008 mass stranding of approximately one hundred melon-
headed whales in a Madagascar lagoon system. An investigation of the 
event indicated that use of a high-frequency mapping system (12-kHz 
multibeam echosounder) was the most plausible and likely initial 
behavioral trigger of the event, while providing the caveat that there 
is no unequivocal and easily identifiable single cause (Southall et 
al., 2013). The investigatory panel's conclusion was based on (1) very 
close temporal and spatial association and directed movement of the 
survey with the stranding event; (2) the unusual nature of such an 
event coupled with previously documented apparent behavioral 
sensitivity of the species to other sound types (Southall et al., 2006; 
Brownell et al., 2009); and (3) the fact that all other possible 
factors considered were determined to be unlikely causes. Specifically, 
regarding survey patterns prior to the event and in relation to 
bathymetry, the vessel transited in a north-south direction on the 
shelf break parallel to the shore, ensonifying large areas of deep-
water habitat prior to operating intermittently in a concentrated area 
offshore from the stranding site. This may have trapped the animals 
between the sound source and the shore, thus driving them towards the 
lagoon system. The investigatory panel systematically excluded or 
deemed highly unlikely nearly all potential reasons for these animals 
leaving their typical pelagic habitat for an area extremely atypical 
for the species (i.e., a shallow lagoon system). Notably, this was the 
first time that such a system has been associated with a stranding 
event. The panel also noted several site- and situation-specific 
secondary factors that may have contributed to the avoidance responses 
that led to the eventual entrapment and mortality of the whales. 
Specifically, shoreward-directed surface currents and elevated 
chlorophyll levels in the area preceding the event may have played a 
role (Southall et al., 2013). The report also notes that prior use of a 
similar system in the general area may have sensitized the animals and 
also concluded that, for odontocete cetaceans that hear well in higher 
frequency ranges where ambient noise is typically quite low, high-power 
active sonars operating in this range may be

[[Page 37473]]

more easily audible and have potential effects over larger areas than 
low frequency systems that have more typically been considered in terms 
of anthropogenic noise impacts. It is, however, important to note that 
the relatively lower output frequency, higher output power, and complex 
nature of the system implicated in this event, in context of the other 
factors noted here, likely produced a fairly unusual set of 
circumstances that indicate that such events likely remain rare and are 
not necessarily relevant to use of lower-power, higher-frequency 
systems more commonly used for high resolution geophysical (HRG) survey 
applications. The risk of similar events recurring may be very low, 
given the extensive use of active acoustic systems used for scientific 
and navigational purposes worldwide on a daily basis and the lack of 
direct evidence of such responses previously reported.
    3. Stress Responses--An animal's perception of a threat may be 
sufficient to trigger stress responses consisting of some combination 
of behavioral responses, autonomic nervous system responses, 
neuroendocrine responses, or immune responses (e.g., Seyle, 1950; 
Moberg 2000). In many cases, an animal's first and sometimes most 
economical (in terms of energetic costs) response is behavioral 
avoidance of the potential stressor. Autonomic nervous system responses 
to stress typically involve changes in heart rate, blood pressure, and 
gastrointestinal activity. These responses have a relatively short 
duration and may or may not have a significant long-term effect on an 
animal's fitness.
    Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that 
are affected by stress--including immune competence, reproduction, 
metabolism, and behavior--are regulated by pituitary hormones. Stress-
induced changes in the secretion of pituitary hormones have been 
implicated in failed reproduction, altered metabolism, reduced immune 
competence, and behavioral disturbance (e.g., Moberg 1987; Blecha 
2000). Increases in the circulation of glucocorticoids are also equated 
with stress (Romano et al. 2004).
    The primary distinction between stress (which is adaptive and does 
not normally place an animal at risk) and ``distress'' is the cost of 
the response. During a stress response, an animal uses glycogen stores 
that can be quickly replenished once the stress is alleviated. In such 
circumstances, the cost of the stress response will not pose serious 
fitness consequences. However, when an animal does not have sufficient 
energy reserves to satisfy the energetic costs of a stress response, 
energy resources must be diverted from other functions. This state of 
distress will last until the animal replenishes its energetic reserves 
sufficiently to restore normal function.
    Relationships between these physiological mechanisms, animal 
behavior, and the costs of stress responses are well-studied through 
controlled experiments and for both laboratory and free-ranging animals 
(e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003; 
Lankford et al., 2005). Stress responses due to exposure to 
anthropogenic sounds or other stressors and their effects on marine 
mammals have also been reviewed (Fair and Becker, 2000; Romano et al., 
2002) and, more rarely, studied in wild populations (e.g., Romano et 
al., 2002). For example, Rolland et al. (2012) found that noise 
reduction from reduced ship traffic in the Bay of Fundy was associated 
with decreased stress in North Atlantic right whales. These and other 
studies lead to a reasonable expectation that some marine mammals will 
experience physiological stress responses upon exposure to acoustic 
stressors and that it is possible that some of these would be 
classified as ``distress.'' In addition, any animal experiencing TTS 
would likely also experience stress responses (NRC, 2003).
    In general, there are few data on the potential for strong, 
anthropogenic underwater sounds to cause non-auditory physical effects 
in marine mammals. Such effects, if they occur at all, will presumably 
be limited to short distances and to activities that extend over a 
prolonged period. The available data do not allow identification of a 
specific exposure level above which non-auditory effects can be 
expected (Southall et al., 2007). There is no definitive evidence that 
any of these effects occur even for marine mammals in close proximity 
to an anthropogenic sound source. In addition, marine mammals that show 
behavioral avoidance of survey vessels and related sound sources, are 
unlikely to incur non-auditory impairment or other physical effects. 
NMFS does not expect that the generally short-term, intermittent, and 
transitory seismic and geophysical surveys creates conditions of long-
term, continuous noise and chronic acoustic exposure leading to long-
term physiological stress responses in marine mammals. While the noise 
from drilling related activities are more continuous and longer term, 
those sounds are generated at a much lower level than the mobile 
sources discussed earlier.
    4. Auditory Masking--Sound can disrupt behavior through masking, or 
interfering with, an animal's ability to detect, recognize, or 
discriminate between acoustic signals of interest (e.g., those used for 
intraspecific communication and social interactions, prey detection, 
predator avoidance, navigation) (Richardson et al., 1995; Erbe et al., 
2016). Masking occurs when the receipt of a sound is interfered with by 
another coincident sound at similar frequencies and at similar or 
higher intensity, and may occur whether the sound is natural (e.g., 
snapping shrimp, wind, waves, precipitation) or anthropogenic (e.g., 
shipping, sonar, seismic exploration) in origin. The ability of a noise 
source to mask biologically important sounds depends on the 
characteristics of both the noise source and the signal of interest 
(e.g., signal-to-noise ratio, temporal variability, direction), in 
relation to each other and to an animal's hearing abilities (e.g., 
sensitivity, frequency range, critical ratios, frequency 
discrimination, directional discrimination, age or TTS hearing loss), 
and existing ambient noise and propagation conditions.
    Under certain circumstances, marine mammals experiencing 
significant masking could also be impaired from maximizing their 
performance fitness in survival and reproduction. Therefore, when the 
coincident (masking) sound is man-made, it may be considered harassment 
when disrupting or altering critical behaviors. It is important to 
distinguish TTS and PTS, which persist after the sound exposure, from 
masking, which occurs during the sound exposure. Because masking 
(without resulting in TS) is not associated with abnormal physiological 
function, it is not considered a physiological effect, but rather a 
potential behavioral effect.
    The frequency range of the potentially masking sound is important 
in determining any potential behavioral impacts. For example, low-
frequency signals may have less effect on high-frequency echolocation 
sounds produced by odontocetes but are more likely to affect detection 
of mysticete communication calls and other potentially important 
natural sounds, such as those produced by surf and some prey species. 
The masking of communication signals by anthropogenic noise may be 
considered as a reduction in the communication space of animals (e.g., 
Clark et al., 2009) and may result in energetic or other costs as 
animals change their vocalization behavior (e.g., Miller et al.

[[Page 37474]]

2000; Foote et al. 2004; Parks et al. 2007; Holt et al. 2009). Masking 
can be reduced in situations where the signal and noise come from 
different directions (Richardson et al. 1995), through amplitude 
modulation of the signal, or through other compensatory behaviors 
(Houser and Moore 2014). Masking can be tested directly in captive 
species (e.g., Erbe 2008) but, in wild populations, it must be either 
modeled or inferred from evidence of masking compensation. There are 
few studies addressing real-world masking sounds likely to be 
experienced by marine mammals in the wild (e.g., Branstetter et al. 
2013).
    Masking affects both senders and receivers of acoustic signals and 
can potentially have long-term chronic effects on marine mammals at the 
population level as well as at the individual level. Low-frequency 
ambient sound levels have increased by as much as 20 dB (more than 
three times in terms of SPL) in the world's ocean from pre-industrial 
periods, with most of the increase from distant commercial shipping 
(Hildebrand 2009). All anthropogenic sound sources, but especially 
chronic and lower-frequency signals (e.g., from vessel traffic), 
contribute to elevated ambient sound levels, thus intensifying masking.
    Marine mammal communications are not likely masked appreciably by 
the sub-profiler or seismic survey's signals given the directionality 
of the signal and the brief period when an individual mammal is likely 
to be within its beam. The probability for conductor pipe driving 
masking acoustic signals important to the behavior and survival of 
marine mammal species is low. Vibratory pile driving is also relatively 
short-term, with rapid oscillations occurring for short durations. It 
is possible that vibratory pile driving resulting from this action may 
mask acoustic signals important to the behavior and survival of marine 
mammal species, but the short-term duration and limited affected area 
will result in insignificant impacts from masking. Any masking event 
that could possibly rise to Level B harassment under the MMPA will 
occur concurrently within the zones of behavioral harassment already 
estimated for vibratory pile and conductor pipe driving, and which have 
already been taken into account in the exposure analysis. Pile driving 
will occur for limited durations across multiple widely dispersed 
sites, thus we do not anticipate masking to significantly affect marine 
mammals.

Ship Strike

    Vessel collisions with marine mammals, or ship strikes, can result 
in death or serious injury of the animal. 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. Superficial strikes may not kill or result in 
the death of the animal. These interactions are typically associated 
with large whales (e.g., fin whales), which are occasionally found 
draped across the bulbous bow of large commercial ships upon arrival in 
port. Although smaller cetaceans are more maneuverable in relation to 
large vessels than are large whales, they may also be susceptible to 
strike. The severity of injuries typically depends on the size and 
speed of the vessel, with the probability of death or serious injury 
increasing as vessel speed increases (Knowlton and Kraus 2001; Laist et 
al. 2001; Vanderlaan and Taggart 2007; Conn and Silber 2013). Impact 
forces increase with speed, as does the probability of a strike at a 
given distance (Silber et al. 2010; Gende et al. 2011).
    Pace and Silber (2005) also found that the probability of death or 
serious injury increased rapidly with increasing vessel speed. 
Specifically, the predicted probability of serious injury or death 
increased from 45 to 75 percent as vessel speed increased from 10 to 14 
kn, and exceeded 90 percent at 17 kn. Higher speeds during collisions 
result in greater force of impact, but higher speeds also appear to 
increase the chance of severe injuries or death through increased 
likelihood of collision by pulling whales toward the vessel (Clyne and 
Kennedy, 1999;). In a separate study, Vanderlaan and Taggart (2007) 
analyzed the probability of lethal mortality of large whales at a given 
speed, showing that the greatest rate of change in the probability of a 
lethal injury to a large whale as a function of vessel speed occurs 
between 8.6 and 15 kt. The chances of a lethal injury decline from 
approximately 80 percent at 15 kt to approximately 20 percent at 8.6 
kt. At speeds below 11.8 kt, the chances of lethal injury drop below 50 
percent, while the probability asymptotically increases toward one 
hundred percent above 15 kt.
    Hilcorp's seismic vessels will travel at approximately 4 knots 
(7.41 km/hour) while towing seismic survey gear and a maximum of 4.5 
knots (8.3 km/hr) while conducting geotechnical and geohazard surveys 
(Faithweather, 2018). At these speeds, both the possibility of striking 
a marine mammal and the possibility of a strike resulting in serious 
injury or mortality are discountable. At average transit speed, the 
probability of serious injury or mortality resulting from a strike is 
less than 50 percent. However, the likelihood of a strike actually 
happening is again discountable. Ship strikes, as analyzed in the 
studies cited above, generally involve commercial shipping, which is 
much more common in both space and time than is geophysical survey 
activity. Jensen and Silber (2004) summarized ship strikes of large 
whales worldwide from 1975-2003 and found that most collisions occurred 
in the open ocean and involved large vessels (e.g., commercial 
shipping). Commercial fishing vessels were responsible for three 
percent of recorded collisions, while no such incidents were reported 
for geophysical survey vessels during that time period.
    It is possible for ship strikes to occur while traveling at slow 
speeds. For example, a hydrographic survey vessel traveling at low 
speed (5.5 kt) while conducting mapping surveys off the central 
California coast struck and killed a blue whale in 2009. The State of 
California determined that the whale had suddenly and unexpectedly 
surfaced beneath the hull, with the result that the propeller severed 
the whale's vertebrae, and that this was an unavoidable event. This 
strike represents the only such incident in approximately 540,000 hours 
of similar coastal mapping activity (p = 1.9 x 10-6; 95% CI = 0-5.5 x 
10-6; NMFS, 2013b). In addition, a research vessel reported a fatal 
strike in 2011 of a dolphin in the Atlantic, demonstrating that it is 
possible for strikes involving smaller cetaceans to occur. In that 
case, the incident report indicated that an animal apparently was 
struck by the vessel's propeller as it was intentionally swimming near 
the vessel. While indicative of the type of unusual events that cannot 
be ruled out, neither of these instances represents a circumstance that 
would be considered reasonably foreseeable or that would be considered 
preventable.
    Although the likelihood of the vessel striking a marine mammal is 
low, we require a robust ship strike avoidance protocol (see 
``Mitigation''), which we believe eliminates any foreseeable risk of 
ship strike. We anticipate that vessel collisions involving a seismic 
data acquisition vessel towing gear, while not impossible, represent 
unlikely, unpredictable events for which there are no preventive 
measures. Given the required mitigation measures, the

[[Page 37475]]

relatively slow speed of the vessel towing gear, the presence of marine 
mammal observers, and the short duration of the survey, we believe that 
the possibility of ship strike is discountable. Further, were a strike 
of a large whale to occur, it is unlikely to result in serious injury 
or mortality. 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.

Stranding

    When a living or dead marine mammal swims or floats onto shore and 
becomes ``beached'' or incapable of returning to sea, the event is a 
``stranding'' (Geraci et al. 1999; Perrin and Geraci 2002; Geraci and 
Lounsbury 2005). The legal definition for a stranding under the MMPA is 
(A) a marine mammal is dead and is (i) on a beach or shore of the 
United States; or (ii) in waters under the jurisdiction of the United 
States (including any navigable waters); or (B) a marine mammal is 
alive and is (i) on a beach or shore of the United States and is unable 
to return to the water; (ii) on a beach or shore of the United States 
and, although able to return to the water, is in need of apparent 
medical attention; or (iii) in the waters under the jurisdiction of the 
United States (including any navigable waters), but is unable to return 
to its natural habitat under its own power or without assistance.
    Marine mammals strand for a variety of reasons, such as infectious 
agents, biotoxicosis, starvation, fishery interaction, ship strike, 
unusual oceanographic or weather events, sound exposure, or 
combinations of these stressors sustained concurrently or in series. 
However, the cause or causes of most strandings are unknown (Eaton, 
1979; Best 1982). Numerous studies suggest that the physiology, 
behavior, habitat relationships, age, or condition of cetaceans may 
cause them to strand or might pre-dispose them to strand when exposed 
to another phenomenon. These suggestions are consistent with the 
conclusions of numerous other studies that have demonstrated that 
combinations of dissimilar stressors commonly combine to kill an animal 
or dramatically reduce its fitness, even though one exposure without 
the other does not produce the same result (Fair and Becker 2000; 
Moberg, 2000; Romero 2004; Sih et al. 2004).
    Use of military tactical sonar has been implicated in several 
stranding events (in specific circumstances), although one stranding 
event was associated with the use of seismic airguns. This event 
occurred in the Gulf of California, coincident with seismic reflection 
profiling by the R/V Maurice Ewing operated by Lamont-Doherty Earth 
Observatory (LDEO) of Columbia University and involved two Cuvier's 
beaked whales (Hildebrand 2004). The vessel had been firing an array of 
20 airguns with a total volume of 8,500 in\3\ (Hildebrand 2004). Most 
known stranding events have involved beaked whales, though a small 
number have involved deep-diving delphinids or sperm whales (e.g., 
Southall et al. 2013). In general, long duration (~1 second) and high-
intensity sounds (>235 dB SPL) have been implicated in stranding events 
(Hildebrand 2004). With regard to beaked whales, mid-frequency sound 
has been implicated in a few specific cases (when causation can be 
determined) (Hildebrand 2004). Although seismic airguns create 
predominantly low-frequency energy, the signal does include a mid-
frequency component. Based on the information presented above, we have 
considered the potential for the survey to result in marine mammal 
stranding and have concluded that, based on the best available 
information, stranding is not expected to occur.

Other Potential Impacts

    Here, we briefly address the potential risks due to entanglement 
and contaminant spills. We are not aware of any records of marine 
mammal entanglement in towed arrays such as those considered here. The 
discharge of trash and debris is prohibited (33 CFR 151.51-77) unless 
it is passed through a machine that breaks up solids such that they can 
pass through a 25-mm mesh screen. All other trash and debris must be 
returned to shore for proper disposal with municipal and solid waste. 
Some personal items may be accidentally lost overboard. However, U.S. 
Coast Guard and Environmental Protection Act regulations require 
operators to become proactive in avoiding accidental loss of solid 
waste items by developing waste management plans, posting informational 
placards, manifesting trash sent to shore, and using special 
precautions such as covering outside trash bins to prevent accidental 
loss of solid waste. There are no meaningful entanglement risks posed 
by the described activity, and entanglement risks are not discussed 
further in this document.
    Marine mammals could be affected by accidentally spilled diesel 
fuel from a vessel associated with survey activities. Quantities of 
diesel fuel on the sea surface may affect marine mammals through 
various pathways: Surface contact of the fuel with skin and other 
mucous membranes, inhalation of concentrated petroleum vapors, or 
ingestion of the fuel (direct ingestion or by the ingestion of oiled 
prey) (e.g., Geraci and St. Aubin, 1980, 1990). However, the likelihood 
of a fuel spill during any particular geophysical survey is considered 
to be remote, and the potential for impacts to marine mammals would 
depend greatly on the size and location of a spill and meteorological 
conditions at the time of the spill. Spilled fuel would rapidly spread 
to a layer of varying thickness and break up into narrow bands or 
windows parallel to the wind direction. The rate at which the fuel 
spreads would be determined by the prevailing conditions such as 
temperature, water currents, tidal streams, and wind speeds. Lighter, 
volatile components of the fuel would evaporate to the atmosphere 
almost completely in a few days. Evaporation rate may increase as the 
fuel spreads because of the increased surface area of the slick. 
Rougher seas, high wind speeds, and high temperatures also tend to 
increase the rate of evaporation and the proportion of fuel lost by 
this process (Scholz et al., 1999). We do not anticipate potentially 
meaningful effects to marine mammals as a result of any contaminant 
spill resulting from the survey activities, and contaminant spills are 
not discussed further in this document.
    Similarly, marine mammals could be affected by spilled hazardous 
materials generated by the drilling process. Large and small quantities 
of hazardous materials, including diesel fuel and gasoline, will be 
handled, transported, and stored following the rules and procedures 
described in the Spill Prevention, Control, and Countermeasure (SPCC) 
Plan. Spills and leaks of oil or wastewater arising from the activities 
that reach marine waters could result in direct impacts to the health 
of exposed marine mammals. Individual marine mammals could show acute 
irritation or damage to their eyes, blowhole or nares, and skin; 
fouling of baleen, which could reduce feeding efficiency; and 
respiratory distress from the inhalation of vapors (Geraci and St. 
Aubin 1990). Long-term impacts from exposure to contaminants to the 
endocrine system could impair health and reproduction (Geraci and St. 
Aubin 1990). Ingestion of contaminants could cause acute irritation to 
the digestive tract, including vomiting and aspiration into the lungs, 
which could result in pneumonia or death (Geraci and St.

[[Page 37476]]

Aubin 1990). However, the measures outlined in Hilcorp's spill plan 
minimize the risk of a spill such that we do not anticipate potentially 
meaningful effects to marine mammals as a result of oil spills from 
this activity nor is take from spills authorized and oil spills are not 
discussed further in this document.

Anticipated Effects on Marine Mammal Habitat

    Effects to Prey--Marine mammal prey varies by species, season, and 
location and, for some, is not well documented. Fish react to sounds 
which are especially strong and/or intermittent low-frequency sounds. 
Short duration, sharp sounds can cause overt or subtle changes in fish 
behavior and local distribution. Hastings and Popper (2005) identified 
several studies that suggest fish may relocate to avoid certain areas 
of sound energy. Additional studies have documented effects of pulsed 
sound on fish, although several are based on studies in support of 
construction projects (e.g., Scholik and Yan 2001, 2002; Popper and 
Hastings 2009). Sound pulses at received levels of 160 dB may cause 
subtle changes in fish behavior, although the behavioral threshold 
currently observed is <150 dB RMA re 1 [mu]Pa. SPLs of 180 dB may cause 
noticeable changes in behavior (Pearson et al. 1992; Skalski et al. 
1992). SPLs of sufficient strength have been known to cause injury to 
fish and fish mortality. The most likely impact to fish from survey 
activities at the project area will be temporary avoidance of the area. 
The duration of fish avoidance of a given area after survey effort 
stops is unknown, but a rapid return to normal recruitment, 
distribution and behavior is anticipated.
    Information on seismic airgun impacts to zooplankton, which 
represent an important prey type for mysticetes, is limited. However, 
McCauley et al. (2017) reported that experimental exposure to a pulse 
from a 150 in\3\ airgun decreased zooplankton abundance when compared 
with controls, as measured by sonar and net tows, and caused a two- to 
threefold increase in dead adult and larval zooplankton. Although no 
adult krill were present, the study found that all larval krill were 
killed after air gun passage. Impacts were observed out to the maximum 
1.2 km range sampled. The reaction of fish to airguns depends on the 
physiological state of the fish, past exposures, motivation (e.g., 
feeding, spawning, migration), and other environmental factors. While 
we agree that some studies have demonstrated that airgun sounds might 
affect the distribution and behavior of some fishes, potentially 
impacting foraging opportunities or increasing energetic costs (e.g., 
Fewtrell and McCauley, 2012; Pearson et al., 1992; Skalski et al., 
1992; Santulli et al., 1999; Paxton et al., 2017), other studies have 
shown no or slight reaction to airgun sounds (e.g., Pena et al., 2013; 
Wardle et al., 2001; Jorgenson and Gyselman, 2009; Cott et al., 2012).
    In general, impacts to marine mammal prey are expected to be 
limited due to the relatively small temporal and spatial overlap 
between the survey and any areas used by marine mammal prey species. 
The activities will occur over a relatively short time period in a 
given area and will occur over a very small area relative to the area 
available as marine mammal habitat in Cook Inlet. We do not have any 
information to suggest the survey area represents a significant feeding 
area for any marine mammal, and we believe any impacts to marine 
mammals due to adverse effects to their prey will be insignificant due 
to the limited spatial and temporal impact of the activities. However, 
adverse impacts may occur to a few species of fish and to zooplankton. 
Packard et al. (1990) showed that cephalopods were sensitive to 
particle motion, not sound pressure, and Mooney et al. (2010) 
demonstrated that squid statocysts act as an accelerometer through 
which particle motion of the sound field can be detected. Auditory 
injuries (lesions occurring on the statocyst sensory hair cells) have 
been reported upon controlled exposure to low-frequency sounds, 
suggesting that cephalopods are particularly sensitive to low-frequency 
sound (Andre et al., 2011; Sole et al., 2013). However, these 
controlled exposures involved long exposure to sounds dissimilar to 
airgun pulses (i.e., 2 hours of continuous exposure to 1-second sweeps, 
50-400 Hz). Behavioral responses, such as inking and jetting, have also 
been reported upon exposure to low-frequency sound (McCauley et al., 
2000b; Samson et al., 2014).
    Indirect impacts from spills or leaks could occur through the 
contamination of lower-trophic-level prey, which could reduce the 
quality and/or quantity of marine mammal prey. In addition, individuals 
that consume contaminated prey could experience long-term effects to 
health (Geraci and St. Aubin 1990). However, the likelihood of spills 
and leaks, as described above, is low. This likelihood, in combination 
with Hilcorp's spill plan to reduce the risk of hazardous material 
spills, is such that its effect on prey is not considered further in 
this document.
    Acoustic Habitat--Acoustic habitat is the soundscape--which 
encompasses all of the sound present in a particular location and time, 
as a whole--when considered from the perspective of the animals 
experiencing it. Animals produce sound for, or listen for sounds 
produced by, conspecifics (communication during feeding, mating, and 
other social activities), other animals (finding prey or avoiding 
predators) and the physical environment (finding suitable habitats, 
navigating). Together, sounds made by animals and the geophysical 
environment (e.g., produced by earthquakes, lightning, wind, rain, 
waves) make up the natural contributions to the total acoustics of a 
place. These acoustic conditions, termed acoustic habitat, are one 
attribute of an animal's total habitat.
    Soundscapes are also defined by, and acoustic habitat influenced 
by, the total contribution of anthropogenic sound. This may include 
incidental emissions from sources such as vessel traffic or may be 
intentionally introduced to the marine environment for data acquisition 
purposes (as in the use of airgun arrays or other sources). 
Anthropogenic noise varies widely in its frequency content, duration, 
and loudness and these characteristics greatly influence the potential 
habitat-mediated effects to marine mammals (please see also the 
previous discussion on masking under ``Acoustic Effects''), which may 
range from local effects for brief periods of time to chronic effects 
over large areas and for long durations. Depending on the extent of 
effects to habitat, animals may alter their communications signals 
(thereby potentially expending additional energy) or miss acoustic cues 
(either conspecific or adventitious). For more detail on these concepts 
see, e.g., Barber et al., 2010; Pijanowski et al. 2011; Francis and 
Barber 2013; Lillis  et al. 2014.
    Problems arising from a failure to detect cues are more likely to 
occur when noise stimuli are chronic and overlap with biologically 
relevant cues used for communication, orientation, and predator/prey 
detection (Francis and Barber 2013). Although the signals emitted by 
seismic airgun arrays are generally low frequency, they will also 
likely be of short duration and transient in any given area due to the 
nature of these surveys. Sub-bottom profiler use is also expected to be 
short term and not concentrated in one location for an extended period 
of time. The activities related to exploratory drilling, while less 
transitory in nature, are anticipated to have less severe effects due 
to lower source levels and therefore smaller disturbance zones than the 
mobile sources considered here. Nonetheless,

[[Page 37477]]

we acknowledge the general addition of multiple sound source types into 
the area, which are expected to have intermittent impacts on the 
soundscape, typically of relatively short duration in any given area.
    In summary, activities associated with the action are not likely to 
have a permanent, adverse effect on any fish habitat or populations of 
fish species or on the quality of acoustic habitat. Thus, any impacts 
to marine mammal habitat are not expected to cause significant or long-
term consequences for individual marine mammals or their populations.

Estimated Take

    This section provides an estimate of the number of incidental takes 
authorized through this rule, which will inform both NMFS' 
consideration of ``small numbers'' and the negligible impact 
determination. The methodology used to calculate estimated take has not 
changed from the proposed rule. Errors in NFMS User Spreadsheet input 
values have been corrected and are reflected in bold font in Table 4. 
Correcting these errors has resulted in different exposure estimates 
for most species than those presented in the proposed rule. The correct 
densities for non-beluga species are now reflected in Table 9. These 
are the densities that were used for the take analysis in the proposed 
rule but were not the values presented in Table 9 in the proposed rule.
    Harassment is the only type of take expected to result from these 
activities. Except with respect to certain activities not pertinent 
here, section 3(18) of the MMPA defines ``harassment'' as: Any act of 
pursuit, torment, or annoyance which (i) has the potential to injure a 
marine mammal or marine mammal stock in the wild (Level A harassment); 
or (ii) has the potential to disturb a marine mammal or marine mammal 
stock in the wild by causing disruption of behavioral patterns, 
including, but not limited to, migration, breathing, nursing, breeding, 
feeding, or sheltering (Level B harassment).
    Authorized takes will primarily be by Level B harassment, as use of 
seismic survey and construction equipment has the potential to result 
in disruption of behavioral patterns for individual marine mammals. 
There is also some potential for auditory injury (Level A harassment) 
to result from equipment such as seismic airguns, primarily for 
mysticetes and high frequency species, because predicted auditory 
injury zones are larger than for mid-frequency species and otariids. 
Auditory injury is unlikely to occur for mid-frequency cetaceans. The 
required mitigation and monitoring measures are expected to minimize 
the severity of such taking to the extent practicable.
    As described previously, no mortality is anticipated or authorized 
for this activity. Below we describe how the take is estimated.
    Generally speaking, we estimate take by considering: (1) Acoustic 
thresholds above which NMFS believes the best available science 
indicates marine mammals will be behaviorally harassed or incur some 
degree of permanent hearing impairment; (2) the area or volume of water 
that will be ensonified above these levels in a day; (3) the density or 
occurrence of marine mammals within these ensonified areas; and, (4) 
and the number of days of activities. We note that while these basic 
factors can contribute to a basic calculation to provide an initial 
prediction of takes, additional information that can qualitatively 
inform take estimates is also sometimes available (e.g., previous 
monitoring results or average group size). Below, we describe the 
factors considered here in more detail and present the take estimate.

Acoustic Thresholds

    Using the best available science, NMFS has developed acoustic 
thresholds that identify the received level of underwater sound above 
which exposed marine mammals will be reasonably expected to experience 
behavioral disturbance (equated to Level B harassment) or to incur PTS 
of some degree (equated to Level A harassment).
    Level B Harassment for non-explosive sources--Though significantly 
driven by received level, the onset of behavioral disturbance from 
anthropogenic noise exposure is also informed to varying degrees by 
other factors related to the source (e.g., frequency, predictability, 
duty cycle), the environment (e.g., bathymetry), and the receiving 
animals (hearing, motivation, experience, demography, behavioral 
context) and can be difficult to predict (Southall et al., 2007, 
Ellison et al., 2012). Based on the available science and the practical 
need to use a threshold based on a factor that is both predictable and 
measurable for most activities, NMFS uses a generalized acoustic 
threshold based on received level to estimate the onset of behavioral 
disturbance rising to the level of Level B Harassment. NMFS predicts 
that marine mammals are likely to experience behavioral disturbance 
sufficient to constitute Level B harassment when exposed to underwater 
anthropogenic noise above received levels of 120 dB re 1 [mu]Pa (rms) 
for continuous (e.g., vibratory pile-driving, drilling) and above 160 
dB re 1 [mu]Pa (rms) for non-explosive impulsive (e.g., seismic 
airguns) or intermittent (e.g., scientific sonar) sources.
    Hilcorp's activity includes the use of continuous (vibratory pile 
driving, water jet) and impulsive (seismic airguns, sub-bottom 
profiler, conductor pipe driving, VSP) sources, and therefore the 120 
and 160 dB re 1 [mu]Pa (rms) are applicable.
    Level A harassment for non-explosive sources--NMFS' Technical 
Guidance for Assessing the Effects of Anthropogenic Sound on Marine 
Mammal Hearing (Version 2.0) (Technical Guidance, 2018) identifies dual 
criteria to assess auditory injury (Level A harassment) to five 
different marine mammal groups (based on hearing sensitivity) as a 
result of exposure to noise from two different types of sources 
(impulsive or non-impulsive). Hilcorp's activity includes the use of 
impulsive (seismic airguns, sub-bottom profiler, conductor pipe 
driving, VSP) and non-impulsive (vibratory pile driving, water jet) 
sources.
    These thresholds for PTS are provided in the table below. The 
references, analysis, and methodology used in the development of the 
thresholds are described in NMFS 2018 Technical Guidance, which may be 
accessed at: https://www.nmfs.noaa.gov/pr/acoustics/guidelines.htm.

 Table 3--Thresholds Identifying the Onset of Permanent Threshold Shift
------------------------------------------------------------------------
                                    PTS onset acoustic thresholds *
        Hearing group         ------------------------------------------
                                   Impulsive          Non-impulsive
------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans.  Cell 1:           Cell 2: LE,LF,24h: 199
                                Lpk,flat: 219     dB.
                                dB; LE,LF,24h:
                                183 dB.
Mid-Frequency (MF) Cetaceans.  Cell 3:           Cell 4: LE,MF,24h: 198
                                Lpk,flat: 230     dB.
                                dB; LE,MF,24h:
                                185 dB.

[[Page 37478]]

 
High-Frequency (HF) Cetaceans  Cell 5:           Cell 6: LE,HF,24h: 173
                                Lpk,flat: 202     dB.
                                dB; LE,HF,24h:
                                155 dB.
Phocid Pinnipeds (PW)          Cell 7:           Cell 8: LE,PW,24h: 201
 (Underwater).                  Lpk,flat: 218     dB.
                                dB; LE,PW,24h:
                                185 dB.
Otariid Pinnipeds (OW)         Cell 9:           Cell 10: LE,OW,24h: 219
 (Underwater).                  Lpk,flat:232      dB.
                                dB; LE,OW,24h:
                                203 dB.
------------------------------------------------------------------------
* Dual metric acoustic thresholds for impulsive sounds: Use whichever
  results in the largest isopeth for calculating PTS onset. If a non-
  impulsive sounds has the potential of exceeding the peak sound
  pressure level thresholds associated with impulsive sounds, these
  thresholds should also be considered.
Note: Peak sound pressure (Lpk) has a reference value of 1 [mu]Pa, and
  cumulative sounds exposure level (LE) has a reference value of
  1[mu]Pa2s. in this Table thresholds are abbreviated to reflect
  American National Standards Institute standards (ANSI 2013). However,
  peak sound pressure is defined by ANSI as incorporating frequency
  weighting, which is not the intent for the Technical Guidance. Hence,
  the subscript ``flat'' is being included to indicate peak sound
  pressure should be flat weighted or unweighted within the generalized
  hearing range. The subscript associated with cumulative sound exposure
  level thresholds indicates the designated marine mammal auditory
  weighting function (LF, MF, HF cetaceans, and PW and OW pinnipeds) and
  that the recommended accumulation period is 24 hours. The cumulative
  sound exposure level thresholds could be exceeded in a multitude of
  ways (i.e., varying exposure levels and durations, duty cycle). When
  possible, is it valuable for action proponents to indicate the
  conditions under which these acoustic thresholds will be exceeded.

Ensonified Area

    Here, we describe operational and environmental parameters of the 
activity that will feed into identifying the area ensonified above the 
acoustic thresholds, which include source levels and transmission loss 
coefficient.
    2D Seismic Survey--The area of ensonification for the 2D seismic 
survey was calculated using the NMFS user spreadsheet tab for mobile 
sources. The in-water source line is 6 km in length and only one line 
will be surveyed each day. Therefore, the line length surveyed each day 
for the 2D seismic survey is 6 km.
    3D Seismic Survey--The area of ensonification for the 3D seismic 
survey was calculated using the NMFS user spreadsheet tab for mobile 
sources. The line length is approximately 27.78 km (15 nm), which will 
take approximately 3.75 hrs to survey at a vessel speed of 4 knots (7.5 
km/hr) with a turn of 1.5 hrs. In a 24-hr period, assuming no delays, 
the survey team will be able to collect data on 4.5 lines or 
approximately 127 km. The distance in between line lengths is 3.7 km (2 
nm), so there will be overlap of the area of Level B harassment 
ensonification, resulting in an overestimation of exposures. Instead, 
the total daily area of ensonification was calculated using GIS. The 
Level B harassment radii were added to each track line estimated to be 
traveled in a 24-hour period, and when there was overlapping areas, the 
resulting polygons were merged to one large polygon to eliminate the 
chance that the areas could be summed multiple times over the same 
area. The results of the overall area are summarized in Table 6 below 
and shown on Figure 19 in the application (only showing Level B 
harassment).
    Geohazard Sub-bottom Profiler for Well Sites--The area of 
ensonification for the sub-bottom profiler used during the geohazard 
surveys for the well sites was calculated by multiplying the distances 
(in km) to the NMFS thresholds by the distance of the line (in km) to 
be surveyed each day. The maximum required monitoring distance from the 
well site per BOEM is 2,400 m (or a total length of 4,800 m in 
diameter) and the minimum transect width is 150 m, so the total maximum 
number of transects to be surveyed is 32 (4,800 m/150 m). The total 
distance to be surveyed is 153.60 km (4.8 km x 32 transects). Assuming 
a vessel speed of 4 knots (7.41 km/hr), it will take approximately 0.65 
hrs (38 minutes) to survey a single transect of 4.8 km (time = 
distance/rate). Assuming the team is surveying for 50 percent of the 
day (or 12 hrs), the total number of days it will take to survey the 
total survey grid is 7.77 days (0.65 hr x 12 hr). Similar to the 3D 
seismic survey, there will be overlap in the Level B harassment 
ensonification of the sound because of the distance in between the 
transects. However, because the area and grid to be surveyed depends on 
the results of the 3D survey and the specific location, NMFS used this 
overestimate for purposes of this rulemaking. The total line length to 
be surveyed per day is 19.76 km (total distance to be surveyed 153.6 
km/total days 7.77).
    Geohazard Sub-bottom Profiler for Pipeline Maintenance--The area of 
ensonification for the sub-bottom profiler used during geohazard 
surveys for the pipeline maintenance was calculated by multiplying the 
distances (in km) to the NMFS thresholds by the distance of the line 
(in km) to be surveyed each day. The assumed transect grid is 300 m by 
300 m with 150 m transect widths, so the total to be surveyed is 2,400 
m (2.4 km). Assuming a vessel speed of 4 knots (7.41 km/hr), it will 
take approximately 0.08 hrs (4.86 min) to survey a single transect. The 
total number of days it will take to survey the grid is 1 day. Similar 
to the 3D seismic survey, there will be overlap of the Level B 
harassment ensonification area because of the distance in between the 
transects. However, because the area and grid to be surveyed depends on 
the results of the 3D survey and the specific location, NMFS uses this 
overestimate for purposes of this rule. The total line length to be 
surveyed per day is 2.4 km.
    Other sources--For stationary sources, area of a circle to the 
relevant Level A or Level B harassment isopleths was used to determine 
ensonified area. These sources include: conductor pipe driving, VSP, 
vibratory sheet pile driving, and water jets. Take estimates for 
conductor pipe driving and vibratory sheet pile driving were 
recalculated from the proposed to the final rule using the most updated 
version of the NMFS User spreadsheet (2018) as minor changes were made 
in the relevant calculations in the spreadsheet from the 2016 version 
originally used by Hilcorp.
    When the NMFS Technical Guidance (2016) was published, in 
recognition of the fact that ensonified area/volume could be more 
technically challenging to predict because of the duration component in 
the new thresholds, we developed a User Spreadsheet (updated in NMFS, 
2018) that includes tools to help predict a simple isopleth that can be 
used in conjunction with marine mammal density or occurrence to help 
predict takes by Level A harassment. We note that because of some of 
the assumptions included in the methods

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used for these tools, we anticipate that isopleths produced are 
typically going to be overestimates of some degree, which may result in 
some degree of overestimate of Level A harassment take. However, these 
tools offer the best way to predict appropriate isopleths when more 
sophisticated 3D modeling methods are not available; and NMFS continues 
to develop ways to quantitatively refine these tools and will 
qualitatively address the output where appropriate. For stationary 
sources such as conductor pipe driving or vibratory pile driving, NMFS 
User Spreadsheet predicts the closest distance at which, if a marine 
mammal remained at that distance the whole duration of the activity, it 
will not incur PTS. For mobile sources such as seismic airguns or sub-
bottom profilers, the User Spreadsheet predicts the closest distance at 
which a stationary animal will not incur PTS if the sound source 
traveled by the animal in a straight line at a constant speed. Some 
changes to duration (number of days of activity) were made in response 
to comments that highlighted some errors in calculation methodology. In 
the proposed rule, exposures on partial days of work were summed in 
error. If work may occur for a half day in one location and a different 
half day in another--two days should be used as the number of days of 
activity, not one. The amount of work proposed has not changed, but the 
characterization of the work as far as number of days required to 
complete has changed. The changes in durations used in the User 
Spreadsheet are outlined below.
    For 2D seismic surveying, 10 days of seismic activity will consist 
of in-water work (remaining 20 days are on land). For 3D seismic 
surveying, duration has been reduced from 90 days to 60 days. VSP 
consists of two days of activity per well, resulting in eight days of 
activity for the OCS wells and four days of activity for the Trading 
Bay wells. Pipe driving lasts three days per well, resulting in 12 days 
of pipe driving for the OCS well and 6 days of pipe driving for the 
Trading Bay wells.
    Inputs used in the User Spreadsheet, and the resulting isopleths 
are reported below (Tables 4, 5, and 6). Transmission loss used for all 
calculation was practical spreading (15 LogR).
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        Table 6--Calculated Distances to NMFS Level B Thresholds
------------------------------------------------------------------------
                      Activity                              Level B
------------------------------------------------------     harassment
                                        Impulsive     ------------------
                                   -------------------   Non-impulsive
                                                      ------------------
                                        160 dB rms         120 dB rms
------------------------------------------------------------------------
2D/3D seismic.....................              7,330  .................
Sub-bottom profiler...............              2,929  .................
Pipe driving......................              1,630  .................
VSP...............................              2,470  .................
Vibratory sheet pile driving......  .................              4,642
Water jet.........................  .................                860
------------------------------------------------------------------------

Marine Mammal Occurrence

    In this section we provide the information about the presence, 
density, or group dynamics of marine mammals that will inform the take 
calculations.
    Beluga whale--Historically, beluga whales were observed in both 
upper and lower Cook Inlet in June and July (Rugh et al. 2000). 
However, between 1993 and 1995, less than 3 percent of all of the 
annual sightings were in the lower inlet, south of the East and West 
Forelands, hardly any (one whale in Tuxedni Bay in 1997 and two in 
Kachemak Bay in 2001) have been seen in the lower inlet during these 
surveys 1996-2016 (Rugh et al. 2005; Shelden et al. 2013, 2015, 2017). 
Because of the extremely low sighting rates, it is difficult to provide 
an accurate estimate of density for beluga whales in the mid and lower 
Cook Inlet region.
    Goetz et al. (2012b) developed a habitat-based model to estimate 
Cook Inlet beluga density based on seasonally collected data. The model 
was based on sightings, depth soundings, coastal substrate type, 
environmental sensitivity index, anthropogenic disturbance, and 
anadromous fish streams to predict densities throughout Cook Inlet. The 
result of this work is a beluga density map of Cook Inlet, which 
predicts spatially explicit density estimates for Cook Inlet belugas. 
Using data from the GIS files provided by NMFS and the different 
project locations, the resulting estimated density is shown in Table 7. 
The water jets will be used on pipelines throughout the middle Cook 
Inlet region, so the higher density for the Trading Bay area was used. 
Densities resulting from this model are summarized in Table 7 below.

  Table 7--Cook Inlet Beluga Whale Density Based on Goetz Habitat Model
------------------------------------------------------------------------
                                                   Beluga whale density
       Project location        Project activity        (ind/km\2\)
------------------------------------------------------------------------
Lower Cook Inlet (OCS).......  3D seismic,                          0.00
                                geohazard, pipe
                                driving.
Lower Cook Inlet (east side).  2D seismic......            0.00-0.011106
Iniskin Bay area.............  Sheet pile                       0.024362
                                driving.
North Cook Inlet Unit........  Geohazard, pipe                  0.001664
                                driving.
Trading Bay area.............  Geohazard, pipe         0.004453-0.015053
                                driving, water
                                jets.
------------------------------------------------------------------------


[[Page 37481]]

    Other Marine Mammals--Density estimates of species other than 
beluga whales were estimated from the NMFS June aerial surveys 
conducted for beluga whales between 2000 and 2016 (Rugh et al. 2005; 
Shelden et al. 2013, 2015, 2017). Although these surveys are only flown 
for a few days in one month, they represent the best available 
relatively long-term dataset for marine mammal sightings in Cook Inlet. 
Table 8 below summarizes the maximum marine mammals observed for each 
year for the survey and area covered. To estimate density, the total 
number of individuals per species sighted during surveys was divided by 
the distance flown on the surveys. The total number of animals observed 
accounts for both lower and upper Cook Inlet, so this density estimate 
is higher than what is anticipated for the lower Cook Inlet area. There 
are no density estimates available for California sea lions for Cook 
Inlet so largest potential group size was used.

 Table 8--Density Estimates for Cook Inlet Beluga Whales in Action Area
------------------------------------------------------------------------
                                      NMFS
         Area/activity             density\1\       Goetz density \2\
------------------------------------------------------------------------
Lower Cook Inlet OCS (3D               0.000593                   0.0000
 seismic, geohazard, pipe
 driving, VSP).................
Lower Cook Inlet--east side (2D        0.000593                 0.011106
 seismic)......................
Lower Cook Inlet--west side            0.000593                 0.024362
 Iniskin (vibratory sheet pile
 driving)......................
Trading Bay Unit (pipe driving,        0.000593                 0.015053
 VSP, geohazard)...............
Middle Cook Inlet (routine             0.000593        0.001664-0.015053
 maintenance: geohazard, water
 jet)..........................
------------------------------------------------------------------------


   Table 9--Density Estimates for Other Marine Mammals in Action Area
------------------------------------------------------------------------
                                                       Estimated density
                       Species                             (# marine
                                                         mammals/km\2\)
------------------------------------------------------------------------
Beluga whale:
    Lower and Middle Cook Inlet \1\..................            0.00006
    Lower Cook Inlet \2\.............................            0.01111
    North Cook Inlet Unit \2\........................            0.00166
    Trading Bay area \2\.............................            0.01505
    Iniskin Peninsula \2\............................            0.02436
Humpback whale.......................................            0.00189
Minke whale..........................................            0.00001
Gray whale...........................................             0.0008
Fin whale............................................            0.00031
Killer whale.........................................            0.00064
Dall's porpoise......................................            0.00016
Harbor porpoise......................................            0.00468
Harbor seal..........................................            0.24871
Steller sea lion.....................................            0.00811
------------------------------------------------------------------------
\1\ NMFS aerial survey combined lower and middle Cook Inlet density.
\2\ Goetz et al. 2012(b) habitat-based model density. No density
  available for California sea lions in Cook Inlet.

Duration

    The duration was estimated for each activity and location. For some 
projects, like the 3D seismic survey, the design of the project is well 
developed; therefore, the duration is well-defined. However, for some 
projects, the duration is not well developed, such as activities around 
the lower Cook Inlet well sites, because the duration depends on the 
results of previous studies and equipment availability. Our assumptions 
regarding these activities, which were used to estimate duration, are 
discussed below.
    2D Seismic--A single vessel is capable of acquiring a source line 
in approximately 1-2 hrs and only one source line will be collected in 
one day to allow for all the node deployments and retrievals, and 
intertidal and land zone shot holes drilling. There are up to 10 source 
lines, so assuming all operations run smoothly, there will only be 2 
hrs per day over 10 days of airgun activity. The duration that was used 
to assess exposures from the 2D seismic survey is 10 days.
    3D Seismic--The total anticipated duration of the survey is 45-60 
days, including delays due to equipment, weather, tides, and marine 
mammal shut downs. The duration that was used to assess exposures from 
the 3D seismic survey is 60 days.
    Geohazard Surveys (Sub-bottom profiler)--Assuming surveying occurs 
50 percent of the day (or 12 hrs), the total number of days it will 
take to survey the total geohazard survey grid for a single well is 
7.77 days. This duration was multiplied by the number of wells per site 
resulting in 31.1 days for the four Lower Cook Inlet OCS wells, 7.7 
days for the North Cook Inlet Unit well, and 15.5 days for the two 
Trading Bay area wells.
    The total number of days it will take to survey the geohazard 
survey grid for a pipeline maintenance is 1 day. This duration was 
multiplied by the number of anticipated surveys per year (high estimate 
of three per year), for a total of three days.
    Drive Pipe--It takes approximately three days to install the drive 
pipe per well with only 25 percent of the day necessary for actual pipe 
driving. This duration was multiplied by the number of wells per site 
resulting in three days for each of the four lower Cook Inlet wells for 
a total of 12 days and a total of six days for the two Trading Bay area 
wells. Drive pipe installation is not part of the activities planned at 
the North Cook Inlet site.
    VSP--It takes approximately two days to perform the VSP per well 
with only 25 percent of the day necessary for actual seismic work. VSP 
is not part of the plugging and abandonment (P&A) activities at the 
North Cook Inlet site. This duration was multiplied by the number of 
wells per site, resulting in

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two days for each of the four lower Cook Inlet wells for a total of 
eight days and four day for the two Trading Bay area wells.
    Vibratory Sheet Pile Driving--The total number of days expected to 
install the sheet pile dock face using vibratory hammers on the rock 
causeway is 14-20 days with only 25 percent of the day for actual pile 
driving. 20 days was used as the duration for the calculation.
    Water jets--Water jets are only used when needed for maintenance; 
therefore, the annual duration was estimated to evaluate exposures. 
Each water jet event was estimated to be 30 minutes or less in 
duration. We acknowledge that due to the short duration of this 
activity, it is possible that take will not occur--however, we are 
including consideration of potential take to conservatively ensure 
coverage for the applicant. It was estimated that a water jet event 
occurs three times a month, resulting in only 1.5 hrs per month of 
water jet operation. Water jets are used during ice- free months, so 
this duration was multiplied by 7 months (May-November) resulting in 21 
days.

Take Calculation and Estimation

    Here we describe how the information provided above is brought 
together to produce a quantitative take estimate. The numbers of each 
marine mammal species that could potentially be exposed to sounds 
associated with the activities that exceed NMFS' acoustic Level A and B 
harassment criteria were estimated per type of activity and per 
location. The specific years when these activities might occur are not 
known at this time, so this method of per activity per location allows 
for flexibility in operations and provides NMFS with appropriate 
information for assessing potential exposures. Individual animals may 
be exposed to received levels above our harassment thresholds more than 
once per day, but NMFS considers animals only ``taken'' once per day. 
Exposures refer to any instance in which an animal is exposed to sound 
sources above NMFS' Level A or Level B harassment thresholds. The 
estimated exposures (without any mitigation) per activity per location 
were calculated by multiplying the density of marine mammals (# of 
marine mammals/km\2\) by the area of ensonification (km\2\) and the 
duration (days per year). These results of these calculations are 
presented in Tables 10 and 11 below.
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    The take estimates by activity and location outlined in Tables 10 
and 11 above indicate the takes that are anticipated from all of the 
activities for

[[Page 37485]]

which take will be authorized across the five-year period covered by 
the rule. It is challenging to specify the activities that will 
definitively occur in a specific year because many of the activities 
are progressive (i.e., they depend on results and/or completion of the 
previous activity). The best estimate of the breakdown of activities 
and their associated takes, by year, are provided in Tables 13-17. The 
maximum number of takes that could be authorized in a particular year 
are specified below in Table 18, based on the largest grouping of 
activities Hilcorp could potentially conduct within a year. The 
scenario in Table 18 is accordingly used to conservatively ensure that 
NMFS can make the necessary annual findings.The most realistic scenario 
over the 5-year period includes 3D seismic surveys in the first season, 
activities for one well in the second season in lower Cook Inlet, as 
well as the plugging and abandonment activities in North Cook Inlet 
Unit and the two wells in the Trading Bay area. For the third season, 
we have included activities for drilling two wells in lower Cook Inlet 
and the final well in the fourth season. Each year, the applicant will 
submit an application for an LOA with the specific details of the 
planned work for that year with estimated take numbers.

           Table 12--Summary of Activities Considered by Year
------------------------------------------------------------------------
             Year                    Activity               Area
------------------------------------------------------------------------
Year 1........................  OCS 3D seismic...  LCI.
                                OCS geohazard of   LCI.
                                 2 wells.
                                Pipeline           MCI.
                                 maintenance
                                 (geohazard,
                                 water jet).
Year 2........................  Pile driving at    LCI (Iniskin).
                                 Iniskin.
                                OCS drilling       LCI.
                                 activities
                                 (geohazard, pipe
                                 driving, VSP) at
                                 up to 2 wells.
                                Trading Bay        TB.
                                 drilling
                                 activities
                                 (geohazard, pipe
                                 driving, VSP) at
                                 2 wells.
                                P&A activities     NCI.
                                 (geohazard) at 1
                                 well.
                                Pipeline           MCI.
                                 maintenance
                                 (geohazard,
                                 water jet).
Year 3........................  OCS drilling       LCI.
                                 activities
                                 (geohazard, pipe
                                 driving, VSP) at
                                 1 well.
                                2D seismic.......  LCI.
                                Pipeline           MCI.
                                 maintenance
                                 (geohazard,
                                 water jet).
Year 4........................  OCS drilling       LCI.
                                 activities
                                 (geohazard, pipe
                                 driving, VSP) at
                                 1 well.
                                Pipeline           MCI.
                                 maintenance
                                 (geohazard,
                                 water jet).
Year 5........................  Pipeline           MCI.
                                 maintenance
                                 (geohazard,
                                 water jet).
------------------------------------------------------------------------
LCI--Lower Cook Inlet Wells, NCI--North Cook Inlet Unit well, TB =
  Trading Bay wells, MCI--Middle Cook Inlet Pipeline Maintenance.

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                                                Table 17--Estimated Exposures for Fifth Year of Activity
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                        Level A harassment                              Level B harassment
                                                         -----------------------------------------------------------------------------------------------
                                                                MCI             MCI                             MCI             MCI
                                                            maintenance     maintenance        Total        maintenance     maintenance        Total
                                                             geohazard      water jets                       geohazard      water jets
--------------------------------------------------------------------------------------------------------------------------------------------------------
Humpback whale..........................................            0.00            0.00            0.00            0.04            0.09            0.13
Minke whale.............................................            0.00            0.00            0.00            0.00            0.00            0.00
Gray whale..............................................            0.00            0.00            0.00            0.00            0.00            0.01
Fin whale...............................................            0.00            0.00            0.00            0.01            0.02            0.02
Killer whale............................................            0.00            0.00            0.00            0.01            0.03            0.04
Beluga whale (NMFS).....................................            0.00            0.00            0.00            0.01            0.03            0.04
Beluga whale (Goetz)....................................            0.00            0.00            0.00            0.00            0.73            0.73
Dall's porpoise.........................................            0.00            0.00            0.00            0.00            0.01            0.01
Harbor porpoise.........................................            0.01            0.00            0.01            0.10            0.23            0.33
Harbor seal.............................................            0.02            0.00            0.02            5.24           12.14           17.38
Steller sea lion........................................            0.00            0.00            0.00            0.17            0.40            0.57
California sea lion.....................................            0.00            0.00            0.00            0.00            0.00            0.00
--------------------------------------------------------------------------------------------------------------------------------------------------------


                             Table 18--Estimated Maximum Exposures That May Be Authorized for Each Species in a Single Year
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Level A harassment              Level B harassment         Total maximum annual takes *
                                                         -----------------------------------------------------------------------------------------------
                         Species                              Annual                          Annual
                                                             estimated     Annual takes      estimated     Annual takes    Annual takes     Percent of
                                                             exposures      authorized       exposures      authorized      authorized      population
--------------------------------------------------------------------------------------------------------------------------------------------------------
Humpback whale..........................................            6.81               7           87.26              90              97           11.21
Minke whale.............................................            0.04               0            0.46               5               5            0.41
Gray whale..............................................            0.29               0            3.68               5               5            0.02
Fin whale...............................................            1.19               1           15.31              15              16            0.51
Killer whale (resident).................................            0.07               0           15.61              20              20            0.85
Killer whale (transient.................................            0.07               0           15.61              20              20            3.41
Beluga whale (NMFS).....................................            0.06               0           27.40              35              35           10.67
Beluga whale (Goetz)....................................            0.02               0           33.71              35              35           10.67
Dall's porpoise.........................................            1.32               1            7.58              10              11            0.01
Harbor porpoise.........................................           37.67              38          216.23             216             254            0.82
Harbor seal.............................................          288.07             288       11,496.15          11,496          11,784           ** 25
Steller sea lion........................................            0.70               1          374.85             375             376            0.74
California sea lion.....................................               0               0            0.00               5               5            0.00
--------------------------------------------------------------------------------------------------------------------------------------------------------
* Total takes across five years for Level A harassment and Level B harassment can be found in Tables 10 and 11 respectively.
** The number of exposures authorized does not equal the number of individuals from the population that may be taken for reasons discussed below.

    Based on the results of the acoustic harassment analysis, Hilcorp 
Alaska is requesting a small number of takes by Level A harassment for 
humpback whales, Dall's porpoises, harbor porpoises, Steller sea lions, 
and harbor seals. Neither Hilcorp nor NMFS anticipate that any of the 
activities will result in mortality or serious injury to marine 
mammals, but these species may be exposed to levels exceeding the Level 
A harassment thresholds. Seals are highly curious and exhibit high 
tolerance for anthropogenic activity, so they are likely to enter 
within the larger Level A harassment isopleths. Porpoises are difficult 
to observe at greater distances and usually only remain in an area for 
a short period of time. The total maximum takes authorized by Level A 
harassment annually are for 7 humpback whales, 1 fin whale, 1 Dall's 
porpoises, 38 harbor porpoises, and 288 harbor seals, and 1 Steller sea 
lion.
    The maximum annual authorized takes by Level B harassment for minke 
and gray whale are rounded up to 5 animals, to account for any 
anomalies of multiple sightings within a year. The maximum annual 
authorized takes by Level B harassment for humpback whales is 90 
animals, although it is not expected to approach this number as 
humpbacks are easily observable during monitoring efforts. The maximum 
annual authorized takes by Level B harassment for killer whales are 
rounded up to 20 animals to allow for multiple sightings of small 
groups. The maximum annual authorized takes by Level B harassment for 
Dall's and harbor porpoise are rounded up to 10 and 216 animals, 
respectively, due to the inconspicuous nature of porpoises. Take 
estimates for Cook Inlet beluga whales were calculated using densities 
from both the Goetz model and NMFS aerial surveys, which result in 
similar exposure estimates. To account for the potential for unseen 
take of Cook Inlet beluga whales, the maximum annual takes authorized 
by Level B harassment at 35 animals.
    The maximum annual authorized takes by Level B harassment for 
harbor seals is 11,496 exposures. The estimated number of instances of 
takes by Level B harassment of 11,496 resulting from the calculations 
outlined above is an overestimate due to the inclusion of haul out 
sites numbers in the underlying density estimate used to calculate 
take. Using the daily ensonified area x number of survey days x density 
method results in a reasonable estimate of the instances of take, but 
likely significantly overestimates the number of individual animals 
expected to be taken. With most species, even this overestimated number 
is still very small, and additional analysis is not really necessary to 
ensure minor impacts. However, because of the number and density of 
harbor seals in

[[Page 37492]]

the area, a more accurate understanding of the number of individuals 
likely taken is necessary to fully analyze the impacts and ensure that 
the total number of harbor seals taken is small.
    As described below, based on monitoring results from the area, it 
is likely that the modeled number of estimated instances of harbor seal 
take referenced above is overestimated. The density estimate from NMFS 
aerial surveys includes harbor seal haulouts far south of the action 
area that may never move to an ensonified area. Further, we believe 
that we can reasonably estimate the comparative number of individual 
harbor seals that will likely be taken, based both on monitoring data, 
operational information, and a general understanding of harbor seal 
habitat use.
    Using the daily ensonified area x number of survey days x density, 
the number of instances of exposure above the 160-dB threshold 
estimated for Hilcorp's activity in Cook Inlet is large. However, when 
we examine monitoring data from previous activities, it is clear this 
number is an overestimate--compared to both aerial and vessel based 
observation efforts. Apache's monitoring report from 2012 details that 
they saw 2,474 harbor seals from 29 aerial flights (over 29 days) in 
the vicinity of the survey during the month of June, which is the peak 
month for harbor seal haulout. In surveying the literature, correction 
factors to account for harbor seals in water based on land counts vary 
from 1.2 to 1.65 (Harvey & Goley, 2011). Using the most conservative 
factor of 1.65 (allowing us to consider that some of the other 
individuals on land may have entered the water at other points in day), 
if Apache saw 2,474 seals hauled out then there were an estimated 1,500 
seals in the water during those 29 days. To account for the limited 
number of surveys (29 surveys), NMFS conservatively multiplied the 
number of seals by 5.5 to estimate the number of seals that might have 
been seen if the aerial surveys were conducted for 160 days. This 
yields an estimate of 8,250 instances of seal exposure in the water, 
which is far less than the exposure estimate resulting from Hilcorp's 
calculations. NMFS further reduced the estimate given the context of 
the activity. The activity with the highest potential take of harbor 
seal according to calculations is 3D seismic surveying, primarily due 
to the high source levels. However, the 3D seismic surveying is 
occurring primarily offshore, which is also the area where they are 
least likely to encounter harbor seals. The calculated exposures from 
3D seismic surveying account for 92 percent of the total calculated 
harbor seal exposures across the five years of the project, accounting 
for a high proportion of the takes allocated to deeper water seismic 
activity which is less likely to spatially overlap with harbor seals. 
That the number of potential instances of exposure is likely less than 
calculated is also supported by the visual observations from Protected 
Species Observers (PSOs) on board vessels. PSOs in Cook Inlet sighted a 
total of 285 seals in water over 147 days of activity, which rises to 
about 310 if adjusted to reflect 160 days of effort. Given the size of 
the disturbance zone for these activities, it is likely that not all 
harbor seals that were exposed were seen by PSOs. However 310 is still 
far less than the estimate given by the density calculations.
    Further, based on the residential nature of harbor seals and the 
number of offshore locations included in Hilcorp's project, where 
harbor seals are unlikely to reside, NMFS estimated the number of 
individual harbor seals exposed, given the instances of exposures. 
Given these multiple methods, as well as the behavioral preferences of 
harbor seals for haulouts in certain parts of the Inlet (Montgomery et 
al, 2007), and high concentrations at haulouts in the lower Inlet, it 
is unreasonable to expect that more than 25 percent of the population, 
or 6,847 individuals, will be taken by Level B harassment during 
Hilcorp's activity. Therefore, we estimate that 6,847 individuals may 
be taken, which equates to 25 percent of the estimated abundance in 
NMFS stock assessment report.

Effects of Specified Activities on Subsistence Uses of Marine Mammals

    The availability of the affected marine mammal stocks or species 
for subsistence uses may be impacted by this activity. The subsistence 
uses that may be affected and the potential impacts of the activity on 
those uses are described below. Measures included in this rule to 
reduce the impacts of the activity on subsistence uses are described in 
the Mitigation section. Last, the information from this section and the 
Mitigation section is analyzed to determine whether the necessary 
findings may be made in the Unmitigable Adverse Impact Analysis and 
Determination section.
    The ADF&G conducted studies to document the harvest and use of wild 
resources by residents of communities on the east and west sides of 
Cook Inlet (Jones and Kostick 2016). Data on wild resource harvest and 
use were collected, including basic information about who, what, when, 
where, how, and how much wild resources are being used to develop 
fishing and hunting opportunities for Alaska residents. Tyonek was 
surveyed in 2013 (Jones et al., 2015), and Nanwalek, Port Graham, and 
Seldovia were surveyed in 2014 (Jones and Kostick 2016). Marine mammals 
were harvested by three (Seldovia, Nanwalek, Port Graham) of the four 
communities but at relatively low rates. The harvests consisted of 
harbor seals, Steller sea lions, and northern sea otters (Enhydra 
lutris), the latter of which is managed by the U.S. Fish and Wildlife 
Service and not mentioned further.

                       Table 19--Marine Mammal Harvest by Tyonek in 2013 and Nikiski, Port Graham, Seldovia, and Nanwalek in 2014
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                            Households                  Number of marine mammals harvested
                                                              Harvest       attempting   ---------------------------------------------------------------
                         Village                           (pounds  per       harvest
                                                              capita)      number  (% of   Harbor  seal    Steller  sea    Northern sea    Beluga  Whale
                                                                            residents)                         lion            otter
--------------------------------------------------------------------------------------------------------------------------------------------------------
Tyonek..................................................               2          6 (6%)               6               0               0               0
Seldovia................................................               1          2 (1%)               5               0               3               0
Nanwalek................................................              11         17 (7%)              22               6               1               0
Port Graham.............................................               8        27 (18%)              16               1              24               0
--------------------------------------------------------------------------------------------------------------------------------------------------------


[[Page 37493]]

    In Tyonek, harbor seals were harvested between June and September 
by 6 percent of the households (Jones et al. 2015). Seals were 
harvested in several areas, encompassing an area stretching 20 miles 
along the Cook Inlet coastline from the McArthur River Flats north to 
the Beluga River. Seals were searched for or harvested in the Trading 
Bay areas as well as from the beach adjacent to Tyonek (Jones et al. 
2015). In Seldovia, the harvest of harbor seals (5 total) occurred 
exclusively in December (Jones and Kostick 2016).
    In Nanwalek, 22 harbor seals were harvested in 2014 between March 
and October, the majority of which occur in April. Nanwalek residents 
typically hunt harbor seals and Steller sea lions at Bear Cove, China 
Poot Bay, Tutka Bay, Seldovia Bay, Koyuktolik Bay, Port Chatam, in 
waters south of Yukon Island, and along the shorelines close to 
Nanwalek, all south of the Petition region (Jones and Kosick 2016).
    According to the results presented in Jones and Kostick (2016) in 
Port Graham, harbor seals were the most frequently used marine mammal; 
tribal members harvested 16 in the survey year. Harbor seals were 
harvested in January, February, July, August, September, November, and 
December. Steller sea lions were used noticeably less and harvested in 
November and December.
    The Cook Inlet beluga whale has traditionally been hunted by Alaska 
Natives for subsistence purposes. For several decades prior to the 
1980s, the Native Village of Tyonek residents were the primary 
subsistence hunters of Cook Inlet beluga whales. During the 1980s and 
1990s, Alaska Natives from villages in the western, northwestern, and 
North Slope regions of Alaska either moved to or visited the south-
central region and participated in the yearly subsistence harvest 
(Stanek 1994). From 1994 to 1998, NMFS estimated 65 whales per year 
were taken in this harvest, including those successfully taken for 
food, and those struck and lost. NMFS has concluded that this number is 
high enough to account for the estimated 14 percent annual decline in 
population during this time (Hobbs et al. 2008). Actual mortality may 
have been higher, given the difficulty of estimating the number of 
whales struck and lost during the hunts. In 1999, a moratorium was 
enacted (Pub. L. 106-31) prohibiting the subsistence take of Cook Inlet 
beluga whales except through a cooperative agreement between NMFS and 
the affected Alaska Native organizations.
    Since the Cook Inlet beluga whale harvest was regulated in 1999 
requiring cooperative agreements, five beluga whales have been struck 
and harvested. Those beluga whales were harvested in 2001 (one animal), 
2002 (one animal), 2003 (one animal), and 2005 (two animals). The 
Native Village of Tyonek agreed not to hunt or request a hunt in 2007, 
when no co-management agreement was to be signed (NMFS 2008). On 
October 15, 2008, NMFS published a final rule that established long-
term harvest limits on the Cook Inlet beluga whales that may be taken 
by Alaska Natives for subsistence purposes (73 FR 60976). That rule 
prohibited harvest for a 5-year period (2008-2012), if the average 
abundance for the Cook Inlet beluga whales from the prior five years 
(2003-2007) is below 350 whales. The 2008 Cook Inlet Beluga Whale 
Subsistence Harvest Final Supplemental Environmental Impact Statement 
(NMFS 2008a) authorizes how many beluga whales can be taken during a 5-
year interval based on the 5-year population estimates and 10-year 
measure of the population growth rate. Based on the 2008-2012 5-year 
abundance estimates, no hunt occurred between 2008 and 2012 (NMFS 
2008a). The previous 5-year period that could have allowed for a 
harvest (2013-2017) required the previous five-year average (2008-2012) 
to be above 350 whales, which it was not and therefore no harvest 
occurred. Based on the current trajectory of the population and annual 
abundance estimates, Cook Inlet beluga whale population abundance is 
not expected to exceed 350 animals for a five year average during the 
duration of these regulations. The Cook Inlet Marine Mammal Council, 
which managed the Alaska Native Subsistence fishery with NMFS, was 
disbanded by a unanimous vote of the Tribes' representatives on June 
20, 2012. No harvest has occurred since then and no harvest is likely 
in 2019 or within the duration of the regulations.
    Residents of the Native Village of Tyonek are the primary 
subsistence users in Knik Arm area (73 FR 60976). No households hunted 
beluga whale locally in Cook Inlet due to conservation concerns (Jones 
et al. 2015). The project should not have any effect because no beluga 
harvest has taken place since 2005, and beluga hunts are not expected 
during the duration of the regulations, based on the abundance estimate 
average requirements discussed above.

Mitigation

    Several changes have been made to mitigation requirements since 
publication of the proposed rule. As discussed in our Comment and 
Response section above, we received public comments raising questions 
about the effectiveness of mitigation guns and power downs at 
minimizing the impacts of seismic surveys on marine mammals. After 
consideration of this evidence, and in maintaining consistency with 
mitigation requirements of other ITAs issued incidental to seismic 
surveys (83 FR 63268), we have removed the requirements for mitigation 
guns and power downs during seismic surveys. A mitigation vessel with 
at least one on-duty PSO will also be required, in addition to PSOs 
aboard the source vessel. Lastly, an additional exclusion zone during 
seismic activity has been added spanning the distance of the Level B 
harassment isopleth at the mouth of the Kasilof River between January 1 
and May 31. Hilcorp is required to abide by all mitigation measures 
described in the Biological Opinion for Hilcorp Alaska and Harvest 
Alaska Oil and Gas Activities, Cook Inlet, Alaska (NMFS, 2019).
    In order to issue an LOA under section 101(a)(5)(A) of the MMPA, 
NMFS must set forth the permissible methods of taking pursuant to such 
activity, and other means of effecting the least practicable impact on 
such species or stock and its habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance, and on 
the availability of such species or stock for taking for certain 
subsistence uses. NMFS regulations require applicants for incidental 
take authorizations to include information about the availability and 
feasibility (economic and technological) of equipment, methods, and 
manner of conducting such activity or other means of effecting the 
least practicable adverse impact upon the affected species or stocks 
and their habitat (50 CFR 216.104(a)(11)).
    In evaluating how mitigation may or may not be appropriate to 
ensure the least practicable adverse impact on species or stocks and 
their habitat, as well as subsistence uses where applicable, we 
carefully consider two primary factors:
    (1) the manner in which, and the degree to which, the successful 
implementation of the measure(s) is expected to reduce impacts to 
marine mammals, marine mammal species or stocks, and their habitat, as 
well as subsistence uses. This considers the nature of the potential 
adverse impact being mitigated (likelihood, scope, range). It further 
considers the likelihood that the measure will be effective if 
implemented (probability of accomplishing the mitigating result if 
implemented as planned), the likelihood of effective implementation

[[Page 37494]]

(probability implemented as planned); and
    (2) the practicability of the measures for applicant 
implementation, which may consider such things as cost, impact on 
operations, and, in the case of a military readiness activity, 
personnel safety, practicality of implementation, and impact on the 
effectiveness of the military readiness activity.

Mitigation for Marine Mammals and Their Habitat

    In their application, Hilcorp proposed and NMFS is requiring 
mitigation measures employed during seismic research surveys authorized 
by NMFS under previous incidental harassment authorizations, as well as 
recommended best practices in Richardson et al. (1995), Pierson et al. 
(1998), Weir and Dolman (2007), Nowacek et al. (2013), Wright (2014), 
and Wright and Cosentino (2015), and has incorporated a suite of 
required mitigation measures into their project description based on 
the above sources. Additional mitigation measures required by NMFS are 
discussed below.
    To reduce the potential for disturbance from acoustic stimuli 
associated with the activities, Hilcorp is required to implement the 
following mitigation measures for marine mammals:
    (1) Vessel-based and shore-based visual mitigation monitoring;
    (2) Establishment of a marine mammal exclusion zone (EZ) and safety 
zone (SZ);
    (3) Shutdown procedures;
    (4) Ramp-up procedures; and
    (5) Vessel strike avoidance measures.
    In addition to the measures proposed by Hilcorp, NMFS requires the 
following mitigation measures: Use of a mitigation vessel to extend 
coverage of PSO monitoring distance, aerial overflights for pre-
clearance before seismic surveys, seasonal closure of the Kasilof River 
during seismic, and seasonal closure of the Susitna River Delta.
    Exclusion and safety zones--The EZ is defined as the area in which 
all operations are shut down in the event a marine mammal enters or is 
about to enter this zone based on distances to the Level A harassment 
threshold or what can be effectively monitored for the species. The SZ 
is an area larger than the EZ and is defined as a focal area beyond the 
standard exclusion zone to be monitored for the presence of protected 
species, and may be considered a Level B harassment. For all 
activities, if a marine mammal for which take is not authorized is seen 
within or entering the SZ, operations will shut down. Any time a beluga 
is sighted during the use of the equipment outlined in Table 20 below, 
activities will shut down. A minimum 10-meter shutdown zone will be 
observed for all in-water construction and heavy machinery.
    The distances for the EZ and SZ for the activities are summarized 
in Table 20 below:

     Table 20--Radii of Exclusion Zone (EZ) and Safety Zone (SZ) for
                          Hilcorp's Activities
------------------------------------------------------------------------
                                          Exclusion zone    Safety zone
                Activity                    (EZ)  radius    (SZ) radius
------------------------------------------------------------------------
2D/3D seismic survey....................           500 m         1,500 m
Sub-bottom profilers....................           100 m         1,500 m
Pipe driving............................           100 m         1,500 m
VSP.....................................           500 m         1,500 m
Sheet pile driving......................           100 m         1,500 m
Water jet...............................            15 m         1,000 m
Hydraulic grinder*......................             N/A             500
Pinger*.................................             N/A             500
Drilling*...............................             N/A             500
Well construction activities*...........             N/A             500
Tug towing rig..........................             N/A           1,500
Dynamic Positioning thrusters*..........             N/A           1,500
Aircraft in route*......................             N/A             500
Aircraft at rig*........................             N/A             500
------------------------------------------------------------------------
* Indicates activities which we do not think results in take and
  therefore take is not proposed to be authorized. These mitigation
  measures are required under the Biological Opinion and have been
  included in this table for clarity of the applicant.

    The distances described in Table 20 are generally smaller than the 
Level B harassment zones from various sources. Level B harassment 
exposures will be recorded and extrapolated based upon the number of 
observed take and the percentage of the Level B harassment zone that 
was not visible. If a PSO is monitoring the EZ and SZ and sees a marine 
mammal outside of those zones but within the Level B harassment 
isopleth, take will be recorded.
    PSO Placement--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 VSP, 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. During 
seismic, at least one PSO must be on duty aboard the mitigation vessel 
in addition to the PSOs on the source vessel.
Seismic Survey Mitigation
    Aircraft--NMFS requires aerial overflights to clear the intended 
area of seismic survey activity of beluga whales on a daily basis. 
Hilcorp will fly over the action area searching for belugas prior to 
ramp up of seismic airguns at the start of daylight hours of each day 
of seismic shooting and ramp up will not commence until the flights 
have confirmed the area appears free of beluga whales. Aerial flights 
are required before starting daylight seismic each day unless weather 
conditions make flying unsafe for aerial personnel. In these cases, 
Hilcorp may ramp up and begin seismic according to the other required 
protocols and the flights must be flown at the earliest safe window. 
This measure only applies to 2D and 3D seismic surveying, not to other 
sound

[[Page 37495]]

sources related to geohazard survey or well construction.
    Clearing the Exclusion Zone--Prior to the start of daily activities 
for which take has been authorized or if activities have been stopped 
for longer than a 30-minute period, the PSOs will ensure the EZ is 
clear of marine mammals for a period of 30 minutes. Clearing the EZ 
means no marine mammals have been observed within the EZ for that 30-
minute period. If any marine mammals have been observed within the EZ, 
ramp up cannot start until the marine mammal has left the EZ or has not 
been observed for a 30-minute period prior to the start of the survey.
    Shutdowns--A shutdown is defined as suspending all airgun 
activities. The operating airguns will be shut down completely if a 
marine mammal is within or enters the EZ. The operations will shut down 
completely if a beluga whale is sighted. The shutdown procedure must be 
accomplished within several seconds (of a ``one shot'' period) of the 
determination that a marine mammal is within or enters the EZ. Airguns 
must be shutdown for turning between transect lines.
    Following a shutdown, airgun activity may be reactivated only after 
the protected species has been observed exiting the applicable EZ. The 
animal will be considered to have cleared the EZ if it:

     Is visually observed to have left the EZ, or
     Has not been seen within the EZ for 15 min in the case of 
pinnipeds and porpoises
     Has not been seen within the EZ for 30 min in the case of 
cetaceans (except for beluga whales which cannot not be seen in the EZ 
or SZ).
    Ramp up--A ``ramp up'' procedure gradually increases airgun volume 
at a specified rate. Ramp up is used at the start of airgun operations, 
including after a shutdown, and after any period greater than 30 
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. During the ramp up, the EZ for the full airgun array 
will be maintained.
    If the complete EZ has not been visible for at least 30 minutes 
prior to the start of operations, ramp up will not commence. This means 
that it will not be permissible to ramp up the 24-gun source from a 
complete shut down in thick fog or at other times when the outer part 
of the EZ is not visible. Ramp up of the airguns will not be initiated 
if a marine mammal is sighted within or entering the EZ at any time.
    Speed or Course Alteration--If a marine mammal is detected outside 
the EZ and, based on its position and relative motion, is likely to 
enter the EZ, the vessel's speed and/or direct course may, when 
practical and safe, be changed. This technique also minimizes the 
effect on the seismic program. The marine mammal activities and 
movements relative to the seismic and support vessels will be closely 
monitored to ensure that the marine mammal does not enter the EZ. If 
the mammal appears likely to enter the EZ, further mitigation actions 
must be taken, i.e., either further course alterations or shutdown of 
the airguns.
    Power downs--In response to public comments on this and other 
seismic incidental take authorizations, it has come to our attention 
that use of power downs may not be effective at reducing impacts to 
marine mammals and may result in more total noise emitted into the 
water. Therefore power downs are not included.
Geohazard Survey Mitigation
    Clearing the Exclusion Zone--Prior to the start of daily activities 
for which take has been authorized or if activities have been stopped 
for longer than a 30-minute period, the PSOs will ensure the EZ is 
clear of marine mammals for a period of 30 minutes. Clearing the EZ 
means no marine mammals have been observed within the EZ for that 30-
minute period. If any marine mammals have been observed within the EZ, 
ramp up cannot start until the marine mammal has left the EZ or has not 
been observed for a 30-minute period prior to the start of the survey.
    Shutdowns--A shutdown is defined as suspending all sub-bottom 
profiler activities. The operating profiler will be shut down 
completely if a marine mammal is within or enters the EZ. The 
operations will shut down completely if a beluga whale is sighted. The 
shutdown procedure must be accomplished within several seconds (of a 
``one shot'' period) of the determination that a marine mammal is 
within or enters the EZ.
    Following a shutdown, sub-bottom profiler activity may be 
reactivated only after the protected species has been observed exiting 
the applicable EZ. The animal will be considered to have cleared the EZ 
if the animal:

     Is visually observed to have left the EZ,
     Has not been seen within the EZ for 15 min in the case of 
pinnipeds and porpoises, or
     Has not been seen within the EZ for 30 min in the case of 
cetaceans (except for beluga whales which cannot not be seen in the EZ 
or SZ).
    Speed or Course Alteration--If a marine mammal is detected outside 
the EZ and, based on its position and relative motion, is likely to 
enter the EZ, the vessel's speed and/or direct course may, when 
practical and safe, be altered. This technique also minimizes the 
effect on the survey program. The marine mammal activities and 
movements relative to the seismic and support vessels will be closely 
monitored to ensure that the marine mammal does not enter the EZ. If 
the mammal appears likely to enter the EZ, further mitigation actions 
must be taken, i.e., either further course alterations or shutdown of 
the airguns.
    Power downs--In response to public comments on this and other 
seismic incidental take authorizations, it has come to our attention 
that use of power downs may not be effective at reducing impacts to 
marine mammals and may result in more total noise emitted into the 
water. Therefore power downs have been removed are not included.
Pipe and Sheet Pile Driving Mitigation
    Soon after the drill rig is positioned on the well head, the 
conductor pipe will be driven as the first stage of the drilling 
operation. Two PSOs (one operating at a time) will be stationed aboard 
the rig during this two to three day operation monitoring the EZ and 
the SZ. The impact hammer operator will be notified to shut down 
hammering operations if a marine mammal is sighted within or enters the 
EZ. A soft start of the hammering will begin at the start of each 
hammering session. The soft start procedure involves initially starting 
with three soft strikes, 30 seconds apart. This delayed-strike start 
alerts marine mammals of the pending hammering activity and provides 
them time to vacate the area. Monitoring will occur during all 
hammering sessions.
    A dock face will be constructed on the rock causeway in Iniskin 
Bay. Two PSOs will be stationed either on a vessel or on land during 
the 14-21 day operation observing an EZ of 4.6 km for beluga whales. 
PSOs will implement similar monitoring and mitigation strategies as for 
the pipe installation.
    For impact hammering, ``soft-start'' technique must be used at the 
beginning of each day's pipe/pile driving activities to allow any 
marine mammal that may be in the immediate area to leave before pile 
driving reaches full energy.

[[Page 37496]]

     Clear the EZ 30 minutes prior to a soft-start to ensure no 
marine mammals are within or entering the EZ.
     Begin impact hammering soft-start with an initial set of 
three strikes from the impact hammer at 40 percent energy, followed by 
a one minute waiting period, then two subsequent 3-strike sets.
     Immediately shut down all hammers at any time a marine 
mammal is detected entering or within the EZ.
     Initial hammering starts will not begin during periods of 
poor visibility (e.g., night, fog, wind).
     Any shutdown due to a marine mammal 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.
Water Jet Mitigation
    A PSO will be present on the dive support vessel when divers are 
using the water jet. Prior to in-water use of the water jet, the EZ 
around the DSV will be established. The water jet will be shut down if 
marine mammals are observed within the EZ.
Beluga Critical Habitat Mitigation
    Hilcorp must not operate noise producing activities within 10 miles 
(16 km) of the mean higher high water (MHHW) line of the Susitna Delta 
(Beluga River to the Little Susitna River) between April 15 and October 
15. The purpose of this mitigation measure is to protect beluga whales 
in the designated critical habitat in this area that is important for 
beluga whale feeding and calving during the spring and fall months. The 
range of the setback required by NMFS was designated to protect this 
important habitat area and also to create an effective buffer where 
sound does not encroach on this habitat. This seasonal exclusion is in 
effect from April 15-October 15. Activities can occur within this area 
from October 16-April 14.

Mitigation for Subsistence Uses of Marine Mammals or Plan of 
Cooperation

    Regulations at 50 CFR 216.104(a)(12) further require Incidental 
Take Authorization applicants conducting activities that take place in 
Arctic waters to provide a Plan of Cooperation or information that 
identifies what measures have been taken and/or will be taken to 
minimize adverse effects on the availability of marine mammals for 
subsistence purposes. A plan must include the following:

     A statement that the applicant has notified and provided 
the affected subsistence community with a draft plan of cooperation;
     A schedule for meeting with the affected subsistence 
communities to discuss planned activities and to resolve potential 
conflicts regarding any aspects of either the operation or the plan of 
cooperation;
     A description of what measures the applicant has taken 
and/or will take to ensure that activities will not interfere with 
subsistence whaling or sealing; and
     What plans the applicant has to continue to meet with the 
affected communities, both prior to and while conducting the activity, 
to resolve conflicts and to notify the communities of any changes in 
the operation.
    Hilcorp Alaska has developed a Stakeholder Engagement Plan (SEP) 
and will implement this plan throughout the duration of the Petition. 
The SEP will help coordinate activities with local stakeholders and 
thus subsistence users, minimize the risk of interfering with 
subsistence hunting activities, and keep current as to the timing and 
status of the subsistence hunts. The Plan is provided in Appendix B of 
Hilcorp's application.
    Hilcorp developed a list of relevant stakeholders who they needed 
to notify of their planned activities. This list included: Commercial 
and sport fishing groups/associations, various Native fisheries and 
entities as it pertains to subsistence fishing and/or hunting, marine 
mammal co-management groups, Cook Inlet Regional Citizens Advisory 
Council, local landowners, government and community organizations, and 
environmental NGOs. Hilcorp contacted the identified stakeholders and 
provided them a summary of their actions and discussed any potential 
concerns and mitigation. The list of contacts, dates of contact, and 
summaries of any concerns raised are available in a spreadsheet 
available on our website at: https://www.fisheries.noaa.gov/action/incidental-take-authorization-hilcorp-alaska-llc-oil-and-gas-activities-cook-inlet-alaska. Hilcorp will be required to abide by 
their stakeholder engagement plan, which will be updated each time 
Hilcorp applies for a LOA, and continue to engage stakeholders 
throughout the five years of activity.
    Based on our evaluation of the applicant's measures, as well as 
other measures considered by NMFS, NMFS has determined that the 
required mitigation measures provide the means effecting the least 
practicable impact on the affected species or stocks and their habitat, 
paying particular attention to rookeries, mating grounds, and areas of 
similar significance, and on the availability of such species or stock 
for subsistence uses.

Monitoring and Reporting

    In order to issue an LOA for an activity, section 101(a)(5)(A) of 
the MMPA states that NMFS must set forth, requirements pertaining to 
the monitoring and reporting of such taking. The MMPA implementing 
regulations at 50 CFR 216.104 (a)(13) indicate that requests for 
authorizations must include the suggested means of accomplishing the 
necessary monitoring and reporting that will result in increased 
knowledge of the species and of the level of taking or impacts on 
populations of marine mammals that are expected to be present in the 
action area. Effective reporting is critical both to compliance as well 
as ensuring that the most value is obtained from the required 
monitoring.
    Monitoring and reporting requirements prescribed by NMFS should 
contribute to improved understanding of one or more of the following:

     Occurrence of marine mammal species or stocks in the area 
in which take is anticipated (e.g., presence, abundance, distribution, 
density);
     Nature, scope, or context of likely marine mammal exposure 
to potential stressors/impacts (individual or cumulative, acute or 
chronic), through better understanding of: (1) Action or environment 
(e.g., source characterization, propagation, ambient noise); (2) 
affected species (e.g., life history, dive patterns); (3) co-occurrence 
of marine mammal species with the action; or (4) biological or 
behavioral context of exposure (e.g., age, calving or feeding areas);
     Individual marine mammal responses (behavioral or 
physiological) to acoustic stressors (acute, chronic, or cumulative), 
other stressors, or cumulative impacts from multiple stressors;
     How anticipated responses to stressors impact either: (1) 
Long-term fitness and survival of individual marine mammals; or (2) 
populations, species, or stocks;
     Effects on marine mammal habitat (e.g., marine mammal prey 
species, acoustic habitat, or other important physical components of 
marine mammal habitat); and
     Mitigation and monitoring effectiveness.
    The PSOs will observe and collect data on marine mammals in and 
around

[[Page 37497]]

the project area for 15 (well activity) or 30 minutes (seismic 
activity) before, during, and for 30 minutes after all of Hilcorp's 
activities for which take has been authorized.

Protected Species Observer Qualifications

    NMFS-approved PSOs must meet the following requirements:
    1. Independent observers (i.e., not construction personnel) are 
required;
    2. At least one observer must have prior experience working as an 
observer;
    3. Other observers may substitute education (undergraduate degree 
in biological science or related field) or training for experience;
    4. Where a team of three or more observers are required, one 
observer should be designated as lead observer or monitoring 
coordinator. The lead observer must have prior experience working as an 
observer; and
    5. NMFS will require submission and approval of observer CVs.

Monitoring Measures

    Sound Source Verification--When site-specific measurements are not 
available for noise sources of concern for acoustic exposure, NMFS 
often requires a sound source verification (SSV) to characterize the 
sound levels, propagation, and to verify the monitoring zones (EZ and 
SZ). Hilcorp Alaska will conduct an SSV for the 3D seismic survey and 
sub-bottom profiler use in lower Cook Inlet. Hilcorp Alaska will work 
with NMFS to ensure the SSV is conducted properly and will provide the 
results to NMFS for review.
    Mitigation vessel--During seismic surveying, Hilcorp will place an 
additional PSO aboard a mitigation vessel. This vessel will be 3,000 m 
(twice the safety zone distance) removed from the source vessel but not 
directly behind the airgun array. This PSO will monitor for the 
occurrence of marine mammals using the same safety zone distances as 
PSOs aboard the source vessel.
    Hilcorp will implement a robust monitoring and mitigation program 
for marine mammals using NMFS-approved PSOs for Petition activities. 
Much of the activities will use vessel-based PSOs, but land- or 
platform-based PSOs may also be used to augment project-specific 
activities. Some details of the monitoring and mitigation program may 
change upon receipt of the individual LOAs issued by NMFS each year.
    The main purposes of PSOs are: To conduct visual watches for marine 
mammals; to serve as the basis for implementation of mitigation 
measures; to document numbers of marine mammals present; to record any 
reactions of marine mammals to Hilcorp's activities; and, to identify 
whether there was any possible effect on accessibility of marine 
mammals to subsistence hunters in Cook Inlet. These observations will 
provide the real-time data needed to implement some of the key 
measures.
    PSOs will be on watch during all daylight periods for project-
specific activities. Generally, work is conducted 24-hrs a day, 
depending on the specific activity.
     For 2D seismic surveys, the airgun operations will be 
conducted during daylight hours.
     For 3D seismic surveys, airgun operations will continue 
during the waning nighttime hours (ranges from 2230-0600 in early April 
to 0100-0300 in mid-May) as long as the full array is operating prior 
to nightfall. Night vision and infrared have been suggested for low 
visibility conditions, but these have not been useful in Cook Inlet or 
other Alaska-based programs. Passive acoustic monitoring has also been 
used in Cook Inlet and is typically required for seismic surveys but 
has not shown to be an effective solution in Cook Inlet's specific 
environmental conditions. A further discussion of previous passive 
acoustic monitoring efforts by several entities in Cook Inlet is 
provided in Section 13 of Hilcorp's application.
     For the sub-bottom profiler, operations will generally be 
conducted during daylight hours but may continue into the low 
visibility period as long as the profiler is operating prior to 
nightfall. Sub-bottom profiler operations may not begin under low 
visibility conditions.
     For pipe driving, VSP, and sheet pile driving, operations 
will generally be conducted during daylight hours.
     Water jet and hydraulic grinder are operated over a 24-
hour period as they are limited to low tide conditions. Activities will 
not start during nighttime but will continue if already started.
    Pre-Activity Monitoring--The exclusion zone will be monitored for 
30 minutes prior to in-water construction/demolition activities. If a 
marine mammal is present within the exclusion zone, the activity will 
be delayed until the animal(s) leave the exclusion zone. Activity will 
resume only after the PSO has determined that, through sighting or by 
waiting (15 minutes for pinnipeds and porpoises, 30 minutes for 
cetaceans) without re-sighting, the animal(s) has moved outside the 
exclusion zone. If a marine mammal is observed within or entering the 
exclusion zone, the PSO who sighted that animal will notify all other 
PSOs and Hilcorp of its presence.
    Post-Activity Monitoring--Monitoring of all zones will continue for 
30 minutes following the completion of the activity.
    For all activities, the PSOs will watch for marine mammals from the 
best available vantage point on the vessel or station. Ideally this 
vantage point is an elevated stable platform from which the PSO has an 
unobstructed 360[deg] view of the water. The PSOs will scan 
systematically with the naked eye and with binoculars. When a mammal 
sighting is made, the following information about the sighting will be 
carefully and accurately recorded:
     Species, group size, age/size/sex categories (if 
determinable), behavior when first sighted and after initial sighting, 
heading (if consistent), bearing and distance from the PSO, apparent 
reaction to activities (e.g., none, avoidance, approach, paralleling), 
closest point of approach, and behavioral pace;
     Time, location, speed, activity of the vessel, sea state, 
ice cover, visibility, and sun glare;
     The positions of other vessel(s) in the vicinity of the 
PSO location; and
     The vessel's position, speed, water depth, sea state, ice 
cover, visibility, and sun glare will also be recorded at the start and 
end of each observation watch, every 30 minutes during a watch, and 
whenever there is a change in any of those variables.
    An electronic database or paper form will be used to record and 
collate data obtained from visual observations.
    The results of the PSO monitoring, including estimates of exposure 
to key sound levels, will be presented in monthly, annual, and final 
reports. Reporting will address the requirements established by NMFS in 
the LOAs. The technical report(s) will include the list below.
     Summaries of monitoring effort: Total hours, total 
distances, and distribution of marine mammals throughout the study 
period compared to sea state, and other factors affecting visibility 
and detectability of marine mammals;
     Analyses of the effects of various factors influencing 
detectability of marine mammals: Sea state, number of observers, and 
fog/glare;
     Species composition, occurrence, and distribution of 
marine mammal sightings including date, water depth, numbers, age/size/
gender categories (when discernable), group sizes, and ice cover; and
     Analyses of the effects of seismic program:
     Sighting rates of marine mammals during periods with and 
without project

[[Page 37498]]

activities (and other variables that could affect detectability);
     Initial sighting distances versus project activity;
     Closest point of approach versus project activity;
     Observed behaviors and types of movements versus project 
activity;
     Numbers of sightings/individuals seen versus project 
activity;
     Distribution around the vessels versus project activity;
     Summary of implemented mitigation measures; and
     Estimates of ``take by harassment.''

Reporting Measures

    Immediate reports will be submitted to NMFS if 30 or more belugas 
are detected over the course of annual operations in the safety and 
exclusion zones during operation of sound sources to evaluate and make 
necessary adjustments to monitoring and mitigation. If the number of 
detected takes for any marine mammal species is met or exceeded, 
Hilcorp will immediately cease survey operations involving the use of 
active sound sources (e.g., airguns and pingers) and notify NMFS Office 
of Protected Resources (OPR).
    1. Monthly Reports--Monthly reports will be submitted to NMFS for 
all months during which in-water seismic activities take place. The 
monthly report will contain and summarize the following information:
     Dates, times, locations, heading, speed, weather, sea 
conditions (including Beaufort sea state and wind force), and 
associated activities during all seismic operations and marine mammal 
sightings.
     Species, number, location, distance from the vessel, and 
behavior of any sighted marine mammals, as well as associated seismic 
activity (number of power-downs and shutdowns), observed throughout all 
monitoring activities.
     An estimate of the number (by species) exposed to the 
seismic activity (based on visual observation) at received levels 
greater than or equal to the NMFS thresholds discussed above with a 
discussion of any specific behaviors those individuals exhibited.
     A description of the implementation and effectiveness of 
the: (i) Terms and conditions of the Biological Opinion's Incidental 
Take Statement (ITS); and (ii) mitigation measures of the LOA. For the 
Biological Opinion, the report must confirm the implementation of each 
Term and Condition, as well as any conservation recommendations, and 
describe their effectiveness for minimizing the adverse effects of the 
action on ESA-listed marine mammals.
    2. Annual Reports--Hilcorp must submit an annual report within 90 
days after each activity year, starting from the date when the LOA is 
issued (for the first annual report) or from the date when the previous 
annual report ended. The annual report will include:
     Summaries of monitoring effort (e.g., total hours, total 
distances, and marine mammal distribution through the study period, 
accounting for sea state and other factors affecting visibility and 
detectability of marine mammals).
     Analyses of the effects of various factors influencing 
detectability of marine mammals (e.g., sea state, number of observers, 
and fog/glare).
     Species composition, occurrence, and distribution of 
marine mammal sightings, including date, water depth, numbers, age/
size/gender categories (if determinable), group sizes, and ice cover.
     Analyses of the effects of survey operations.
     Sighting rates of marine mammals during periods with and 
without seismic survey activities (and other variables that could 
affect detectability), such as: (i) Initial sighting distances versus 
survey activity state; (ii) closest point of approach versus survey 
activity state; (iii) observed behaviors and types of movements versus 
survey activity state; (iv) numbers of sightings/individuals seen 
versus survey activity state; (v) distribution around the source 
vessels versus survey activity state; and (vi) numbers of animals 
detected in the harassment/safety zone.
     NMFS will review the draft annual reports. Hilcorp must 
then submit a final annual report to the Chief, Permits and 
Conservation Division, Office of Protected Resources, NMFS, within 30 
days after receiving comments from NMFS on the draft annual report. If 
NMFS decides that the draft annual report needs no comments, the draft 
report will be considered to be the final report.
    3. Final Report--Hilcorp will submit a final report, within 90 days 
of project completion at the end of the five-year period. This report 
will:
     Summarize the activities undertaken and the results 
reported in all previous reports;
     Assess the impacts to marine mammals and their habitat;
     Assess the cumulative impacts on marine mammals from the 
activities specified in in this rule; and
     State the date(s), location(s), and findings of any 
research activities related to monitoring the effects on noise-
producing oil and gas activities on marine mammal populations.
    4. Discovery of Injured or Dead Marine Mammals--In the event that 
personnel involved in the survey activities covered by the 
authorization discover an injured or dead marine mammal, Hilcorp must 
report the incident to the Office of Protected Resources (OPR), NMFS 
and to the Alaska Regional stranding coordinator as soon as feasible. 
The report must include the following information:
     Time, date, and location (latitude/longitude) of the first 
discovery (and updated location information if known and applicable);
     Species identification (if known) or description of the 
animal(s) involved;
     Condition of the animal(s) (including carcass condition if 
the animal is dead);
     Observed behaviors of the animal(s), if alive;
     If available, photographs or video footage of the 
animal(s); and
     General circumstances under which the animal was 
discovered.
    Vessel Strike--In the event of a ship strike of a marine mammal by 
any vessel involved in the activities covered by the authorization, 
Hilcorp must report the incident to OPR, NMFS and to regional stranding 
coordinator as soon as feasible. The report must include the following 
information:
     Time, date, and location (latitude/longitude) of the 
incident;
     Species identification (if known) or description of the 
animal(s) involved;
     Vessel's speed during and leading up to the incident;
     Vessel's course/heading and what operations were being 
conducted (if applicable);
     Status of all sound sources in use;
     Description of avoidance measures/requirements that were 
in place at the time of the strike and what additional measures were 
taken, if any, to avoid strike;
     Environmental conditions (e.g., wind speed and direction, 
Beaufort sea state, cloud cover, visibility) immediately preceding the 
strike;
     Estimated size and length of animal that was struck;
     Description of the behavior of the marine mammal 
immediately preceding and following the strike;
     If available, description of the presence and behavior of 
any other marine mammals immediately preceding the strike;
     Estimated fate of the animal (e.g., dead, injured but 
alive, injured and moving, blood or tissue observed in the water, 
status unknown, disappeared); and

[[Page 37499]]

     To the extent practicable, photographs or video footage of 
the animal(s).
    Actions to Minimize Additional Harm to Live-Stranded (or Milling) 
Marine Mammals--In the event of a live stranding (or near-shore 
atypical milling) event within 50 km of the survey operations, where 
the NMFS stranding network is engaged in herding or other interventions 
to return animals to the water, the Director of OPR, NMFS (or designee) 
will advise the Hilcorp of the need to implement shutdown procedures 
for all active acoustic sources operating within 50 km of the 
stranding. Shutdown procedures for live stranding or milling marine 
mammals include the following:
     If at any time, the marine mammals die or are euthanized, 
or if herding/intervention efforts are stopped, the Director of OPR, 
NMFS (or designee) will advise Hilcorp that the shutdown around the 
animals' location is no longer needed.
     Otherwise, shutdown procedures will remain in effect until 
the Director of OPR, NMFS (or designee) determines and advises Hilcorp 
that all live animals involved have left the area (either of their own 
volition or following an intervention).
     If further observations of the marine mammals indicate the 
potential for re-stranding, additional coordination with Hilcorp will 
be required to determine what measures are necessary to minimize that 
likelihood (e.g., extending the shutdown or moving operations farther 
away) and to implement those measures as appropriate.
    Shutdown procedures are not related to the investigation of the 
cause of the stranding and their implementation is not intended to 
imply that the specified activity is the cause of the stranding. 
Rather, shutdown procedures are intended to protect marine mammals 
exhibiting indicators of distress by minimizing their exposure to 
possible additional stressors, regardless of the factors that 
contributed to the stranding.

Negligible Impact Analysis and Determination

    NMFS has defined negligible impact as an impact resulting from the 
specified activity that cannot be reasonably expected to, and is not 
reasonably likely to, adversely affect the species or stock through 
effects on annual rates of recruitment or survival (50 CFR 216.103). A 
negligible impact finding is based on the lack of likely adverse 
effects on annual rates of recruitment or survival (i.e., population-
level effects). An estimate of the number of takes alone is not enough 
information on which to base an impact determination. In addition to 
considering estimates of the number of marine mammals that might be 
``taken'' through harassment, NMFS considers other factors, such as the 
likely nature of any responses (e.g., intensity, duration), the context 
of any responses (e.g., critical reproductive time or location, 
migration), as well as effects on habitat, and the likely effectiveness 
of the mitigation. We also assess the number, intensity, and context of 
estimated takes by evaluating this information relative to population 
status. Consistent with the 1989 preamble for NMFS's implementing 
regulations (54 FR 40338; September 29, 1989), the impacts from other 
past and ongoing anthropogenic activities are incorporated into this 
analysis via their impacts on the environmental baseline (e.g., as 
reflected in the regulatory status of the species, population size and 
growth rate where known, ongoing sources of human-caused mortality, or 
ambient noise levels).
    Given the nature of activities, required mitigation and related 
monitoring, no serious injuries or mortalities are anticipated to occur 
as a result of Hilcorp's oil and gas activities in Cook Inlet, and none 
are authorized. The number of takes that are anticipated and authorized 
are expected to be limited mostly to short-term Level B harassment, 
although some PTS may occur. The seismic airguns and other sound 
sources do not operate continuously over a 24-hour period. Rather the 
airguns are operational for a few hours at a time with breaks in 
between, as surveys can only be conducted during slack tides, totaling 
a maximum of 12 hours a day for the most frequently used equipment. 
Sources other than airguns are likely to be used for much shorter 
durations daily than the 12 potential hours of airgun use.
    Cook Inlet beluga whales, the Mexico DPS of humpback whales, fin 
whales, and the western stock of Steller sea lions are listed as 
endangered under the ESA. These stocks are also considered depleted 
under the MMPA. Beluga-specific mitigation measures, such as shutting 
down whenever beluga whales are sighted by PSOs and an exclusion zone 
at the Susitna River Delta months of high beluga concentrations, aim to 
minimize the effects of this activity on the population. Zerbini et al. 
(2006) estimated rates of increase of fin whales in coastal waters 
south of the Alaska, and data from Calambokidis et al. (2008) suggest 
the population of humpback whales by also be increasing. Steller sea 
lion trends for the western stock are variable throughout the region 
with some decreasing and others remaining stable or even indicating 
slight increases. The other species that may be taken by harassment 
during Hilcorp's oil and gas program are not listed as threatened or 
endangered under the ESA nor as depleted under the MMPA.
    Odontocete (including Cook Inlet beluga whales, killer whales, and 
harbor porpoises) reactions to seismic energy pulses are usually 
assumed to be limited to shorter distances from the airgun(s) than are 
those of mysticetes, in part because odontocete low-frequency hearing 
is assumed to be less sensitive than that of mysticetes. When in the 
Canadian Beaufort Sea in summer, belugas appear to be fairly responsive 
to seismic energy, with few being sighted within 10-20 km (6-12 mi) of 
seismic vessels during aerial surveys (Miller et al., 2005). However, 
as noted above, Cook Inlet belugas are more accustomed to anthropogenic 
sound than beluga whales in the Beaufort Sea. Therefore, the results 
from the Beaufort Sea surveys may be less applicable to potential 
reactions of Cook Inlet beluga whales. Also, due to the dispersed 
distribution of beluga whales in Cook Inlet during winter and the 
concentration of beluga whales in upper Cook Inlet from late April 
through early fall (i.e., far north of the seismic surveys), belugas 
will likely occur in small numbers in the majority of Hilcorp's survey 
area during the majority of Hilcorp's annual operational timeframe.
    Taking into account the mitigation measures that are planned, 
effects on cetaceans are generally expected to be restricted to 
avoidance of a limited area around the survey operation and short-term 
changes in behavior, such as changes in direction of travel, temporary 
avoidance, or alteration of behaviors such as breeding or feeding, 
falling within the MMPA definition of ``Level B harassment.'' It is 
possible that Level A harassment take of marine mammals from sound 
sources such as seismic airguns may also occur. The duration of 
exposure from acoustic sources that we think have the potential to 
result in PTS are relatively short term and spatially limited, as 
compared to the extent of the Level B harassment zone. These relatively 
small PTS zones, combined with the short duration of potential exposure 
and the transitory nature of marine mammals most likely to be in the 
vicinity of the seismic vessel, indicate that the degree of PTS to any 
particular individual marine mammal would be small. Due to the short 
term duration of activities in any given area and the small geographic 
area in which

[[Page 37500]]

Hilcorp's activities will be occurring at any one time, it is unlikely 
that these activities will affect reproduction or survival of cetaceans 
in Cook Inlet. Animals are not expected to permanently abandon any area 
that is surveyed, and any behaviors that are interrupted during the 
activity are expected to resume once the activity ceases. Only a small 
portion of marine mammal habitat will be affected at any time, and 
other areas within Cook Inlet will be available for necessary 
biological functions including breeding, foraging, and mating. In 
addition, NMFS seasonally restricts seismic survey operations in 
locations known to be important for beluga whale feeding, calving, or 
nursing. One of the primary locations for these biological life 
functions occur in the Susitna Delta region of upper Cook Inlet. NMFS 
will implement a 16 km (10 mi) seasonal exclusion from activities for 
which take has been authorized in this region from April 15 to October 
15 annually. The highest concentrations of belugas are typically found 
in this area from early May through September each year. NMFS has 
incorporated a 2-week buffer on each end of this seasonal use timeframe 
to account for any anomalies in distribution and marine mammal usage. 
Additionally, NMFS has included a seasonal closure from January through 
May at the mouth of the Kasilof River, where belugas have been reported 
to aggregate primarily in the month of April.
    Mitigation measures, such as dedicated marine mammal observers, and 
shutdowns when marine mammals are seen within defined ranges, are 
designed both to further reduce short-term reactions and minimize any 
effects on hearing sensitivity. In cases of PTS, for the reasons 
outlined above including limited duration of exposure and the 
transitory nature of marine mammals likely to occur close to the 
seismic vessel, the severity of PTS expected to occur in a few 
individual marine mammals would be low. In cases of Level B harassment, 
the effects of these activities are expected to be short-term, with no 
lasting biological consequence. Therefore, the exposure of cetaceans to 
sounds produced by Hilcorp's oil and gas activities is not anticipated 
to have an effect on annual rates of recruitment or survival of the 
affected species or stocks.
    Some individual pinnipeds may be exposed to sound from the 
activities more than once during the timeframe of the project. Taking 
into account the mitigation measures that are planned, effects on 
pinnipeds are generally expected to be restricted to avoidance of a 
limited area around the survey operation and short-term changes in 
behavior, falling within the MMPA definition of ``Level B harassment,'' 
although some pinnipeds may approach close enough to sound sources 
undetected and incur PTS. Due to the solitary nature of pinnipeds in 
water, this is expected to be a small number of individuals and the 
calculated distances to the PTS thresholds incorporate a relatively 
long duration, making them conservative; however, the impacts of the 
authorized Level A harassment takes have been analyzed and, as 
indicated previously, due to the anticipated relatively shorter 
duration of exposure, any take by PTS would be expected to be of a 
lower degree. Animals are not expected to permanently abandon any area 
that is surveyed, and any behaviors that are interrupted during the 
activity are expected to resume once the activity ceases. Only a small 
portion of pinniped habitat will be affected at any time, and other 
areas within Cook Inlet will be available for necessary biological 
functions. In addition, the areas where the activities will take place 
are largely offshore and not known to be biologically important areas 
for pinniped populations. Therefore, the exposure of pinnipeds to 
sounds produced by this phase of Hilcorp's activity is not anticipated 
to have an effect on annual rates of recruitment or survival on those 
species or stocks.
    The addition of multiple source and supply vessels, and noise due 
to vessel operations associated with the activities, will not be 
outside the present experience of marine mammals in Cook Inlet, 
although levels may increase locally. Given the large number of vessels 
in Cook Inlet and the apparent habituation to vessels by Cook Inlet 
beluga whales and the other marine mammals that may occur in the area, 
the aggregate vessel activity and its associated noise is not expected 
to have effects that could cause significant or long-term consequences 
for individual marine mammals or their populations.
    Potential impacts to marine mammal habitat were discussed 
previously in this document (see the ``Anticipated Effects on Habitat'' 
section). As noted above, only one year of activity should reach the 
maximum annual authorized takes, which are the numbers used to make our 
findings in this rulemaking. Although some disturbance is possible to 
food sources of marine mammals, the impacts are anticipated to be minor 
enough as to not affect the fitness of individuals in a manner that 
would accrue to impacts on annual rates of recruitment or survival of 
marine mammals in the area. Based on the size of Cook Inlet where 
feeding by marine mammals occurs versus the localized area of the 
marine survey activities, any missed feeding opportunities in the 
direct project area will be minor based on the fact that other feeding 
areas exist elsewhere. Additionally, operations will not occur in the 
primary beluga feeding and calving habitat during times of high use by 
those animals. The mitigation measure of limiting activities around the 
Susitna Delta will also protect beluga whale prey and their foraging 
habitat.
    In summary and as described above, the following factors primarily 
support our determination that the impacts resulting from this activity 
are not expected to adversely affect the species or stock through 
effects on annual rates of recruitment or survival:
     No mortality is anticipated or authorized;
     Any small number of PTS takes incurred would be expected 
to be of a lower degree of hearing sensitivity loss;
     A majority of the impacts to marine mammals would be in 
the form of short-term, Level B harassment;
     Mitigation for beluga whales is extensive, including 
shutdowns at any distance and exclusion zones and avoiding exposure 
during critical foraging periods around the Susitna Delta;
     Location of activities is offshore which minimizes effects 
of activity on resident pinnipeds at haulouts,
     A large concentration of seismic surveying in the lower 
portions of Cook Inlet will extend into open water where densities of 
marine mammals are less than other parts of the Inlet; and
     Comprehensive land, sea, and aerial-based monitoring will 
maximizing marine mammal detection rates as well as acoustic SSV to 
verify exposure levels.
    Based on the analysis contained herein of the likely effects of the 
specified activity on marine mammals and their habitat, and taking into 
consideration the implementation of the required monitoring and 
mitigation measures, NMFS finds that the total marine mammal take from 
the activity will have a negligible impact on all affected marine 
mammal species or stocks.

Small Numbers

    As noted above, only small numbers of incidental take may be 
authorized under section 101(a)(5)(A) of the MMPA for specified 
activities other than military readiness activities. The MMPA does not 
define small numbers and so, in practice, NMFS compares the number of 
individuals taken within a year to the most appropriate estimation of

[[Page 37501]]

abundance of the relevant species or stock in our determination of 
whether an authorization is limited to small numbers of marine mammals. 
Additionally, other qualitative factors may be considered in the 
analysis, such as the temporal or spatial scale of the activities.
    As described above in Table 18, the takes authorized represent less 
than 25 percent of any stock of population in the year of maximum 
activity. The authorized takes represent less than 10 percent of the 
stock abundance for nine species of marine mammals known to occur in 
Cook Inlet, Alaska. For the North Pacific stock of humpback whales, the 
authorized take of 97 individuals represents 11.21 percent of the 
stock. For Cook Inlet beluga whales, authorized take of 35 individuals 
annually represent 10.67 percent of the stock.
    The exposures above the harassment threshold calculated for harbor 
seals would represent 43 percent of the Cook Inlet/Shelikof stock of 
approximately 27,386 animals if each instance of exposure represented a 
unique individual; however, that is not the case. The mathematical 
calculation that resulted in 11,496 Level B harassment exposures does 
not account for other factors that, when considered appropriately, 
suggest that far fewer individuals will be taken. The species' coastal 
nature, affinity for haulout sites in other portions of the Inlet, and 
absence during previous seismic surveys suggests that the number of 
individuals seals exposed to noise at or above the Level B harassment 
threshold, which likely represent repeated exposures of the same 
individual, is at a low enough level for NMFS to consider small.
    In our Take Estimation section above, we describe the qualitative 
factors that suggest calculated exposure, specifically for seismic 
airgun use or drilling activities located offshore, is an overestimate 
of the number of individuals likely to occur within the Level A or 
Level B harassment zones.
    Previous monitoring reports also help to provide context for the 
number of individual harbor seals likely to be taken. In 2012, 
SAExploration Inc. observers detected fewer than 300 seals during 116 
days of operations, with 100 seals the most seen at once, at a river 
mouth, hauled out, not in the water or exposed to seismic activity. In 
2014, Apache observers saw an estimated 613 individuals in 82 days of 
operation, mostly during non-seismic periods. Most harbor seals were 
recorded from the land station, not source vessels. Of the 492 groups 
of harbor seals seen, 441 were seen during non-seismic operations. The 
number of harbor seals observed and reported within the take zone in 
previous surveys suggests that the predicted instances of take of 
harbor seals for Apache's surveys may be overestimates. Further, the 
known distribution of this harbor seal stock, including the known 
preference for haulouts at river mouths, suggest that the number of 
exposures calculated through the daily ensonified method is a notable 
overestimate of the number of individual seals likely to be taken. When 
the previously described factors regarding the spatiotemporal 
distribution of this harbor seal stock throughout its range are 
considered, we believe that it is a reasonable prediction that not more 
than 25% of the individuals in the population will be taken by Level A 
or Level B harassment.
    Based on the analysis contained herein of the activity (including 
the required mitigation and monitoring measures) and the anticipated 
take of marine mammals, NMFS finds that small numbers of marine mammals 
will be taken relative to the population size of the affected species 
or stocks.

Unmitigable Adverse Impact Analysis and Determination

    In order to issue an ITA, NMFS must find that the specified 
activity will not have an ``unmitigable adverse impact'' on the 
subsistence uses of the affected marine mammal species or stocks by 
Alaskan Natives. NMFS has defined ``unmitigable adverse impact'' in 50 
CFR 216.103 as an impact resulting from the specified activity: (1) 
That is likely to reduce the availability of the species to a level 
insufficient for a harvest to meet subsistence needs by: (i) Causing 
the marine mammals to abandon or avoid hunting areas; (ii) Directly 
displacing subsistence users; or (iii) placing physical barriers 
between the marine mammals and the subsistence hunters; and (2) that 
cannot be sufficiently mitigated by other measures to increase the 
availability of marine mammals to allow subsistence needs to be met.
    The project is unlikely to affect beluga whale harvests because no 
beluga harvest will take place in 2019, nor is one likely to occur in 
the other years that covered by the 5-year regulations and associated 
LOAs. This assumption is largely based on the lack of increased 
abundance of Cook Inlet beluga whales such that a 5-year population 
estimate average would exceed 350 individuals. Additionally, the action 
area is not an important native subsistence site for other subsistence 
species of marine mammals. Because of the relatively small number of 
marine mammals harvested in Cook Inlet, the number affected by the 
action is expected to be extremely low. To further minimize any 
potential effects of their action on subsistence activities, Hilcorp is 
required to detail how they have engaged with stakeholders to discuss 
potential concerns regarding their planned activities, as well as how 
they will continue to engage with stakeholder during the course of 
their project. Hilcorp has outlined their communication plan for 
engaging with subsistence users in their Stakeholder Engagement Plan. 
Hilcorp will be required to abide by this plan and the plan will be 
updated every time Hilcorp applies for a LOA. Therefore, because the 
action will result in only temporary disturbances, the action will not 
impact the availability of these other marine mammal species for 
subsistence uses.
    The timing and location of subsistence harvest of Cook Inlet harbor 
seals may coincide with Hilcorp's project but, because this subsistence 
hunt is conducted opportunistically and at such a low level (NMFS, 
2013c), Hilcorp's program is not expected to have an impact on the 
subsistence use of harbor seals. Hilcorp's list of contacts who were 
notified about their activities includes communities and individuals 
who participate in subsistence hunting of harbor seals. Hilcorp will 
continue to coordinate with the identified stakeholders to ensure there 
are no conflicts between their activities and harbor seal subsistence 
hunts throughout the duration of these regulations, as required in the 
regulations and described in Hilcorp's Stakeholder Engagement Plan.
    NMFS anticipates that any effects from Hilcorp's activities on 
marine mammals, especially harbor seals and Cook Inlet beluga whales, 
which are or have been taken for subsistence uses, will be short-term, 
site specific, and limited to inconsequential changes in behavior and 
mild stress responses. NMFS does not anticipate that the authorized 
taking of affected species or stocks will reduce the availability of 
the species to a level insufficient for a harvest to meet subsistence 
needs by: (1) Causing the marine mammals to abandon or avoid hunting 
areas; (2) directly displacing subsistence users; or (3) placing 
physical barriers between the marine mammals and the subsistence 
hunters. And any such potential reductions could be sufficiently 
mitigated by other measures to increase the availability of marine 
mammals to allow subsistence needs to be met. Based on the description 
of the specified activity, the measures described to minimize adverse 
effects

[[Page 37502]]

on the availability of marine mammals for subsistence purposes, and the 
required mitigation and monitoring measures, NMFS has determined that 
there will not be an unmitigable adverse impact on subsistence uses 
from Hilcorp's activities.

Adaptive Management

    The regulations governing the take of marine mammals incidental to 
Hilcorp's oil and gas activities will contain an adaptive management 
component.
    The reporting requirements associated with this rule are designed 
to provide NMFS with monitoring data from the previous year to allow 
consideration of whether any changes are appropriate. The use of 
adaptive management allows NMFS to consider new information from 
different sources to determine (with input from Hilcorp regarding 
practicability) on an annual basis if mitigation or monitoring measures 
should be modified (including additions or deletions). Mitigation or 
monitoring measures could be modified if new data suggests that such 
modifications will have a reasonable likelihood more effectively 
achieving the goals of the mitigation and monitoring and if the 
measures are practicable.
    The following are some of the possible sources of applicable data 
to be considered through the adaptive management process: (1) Results 
from monitoring reports, as required by MMPA authorizations; (2) 
results from general marine mammal and sound research; and (3) any 
information which reveals that marine mammals may have been taken in a 
manner, extent, or number not authorized by these regulations or 
subsequent LOAs.

Endangered Species Act (ESA)

    Section 7(a)(2) of the Endangered Species Act of 1973 (ESA: 16 
U.S.C. 1531 et seq.) requires that each Federal agency insure that any 
action it authorizes, funds, or carries out is not likely to jeopardize 
the continued existence of any endangered or threatened species or 
result in the destruction or adverse modification of designated 
critical habitat. To ensure ESA compliance for the issuance of ITAs, 
NMFS consults internally, in this case with the Alaska Protected 
Resources Division Office, whenever we propose to authorize take for 
endangered or threatened species. NMFS is authorizing take of Cook 
Inlet beluga whale, Northeastern Pacific stock of fin whales, Western 
North Pacific, Hawaii, and Mexico DPS of humpback whales, and western 
DPS of Steller sea lions, which are listed under the ESA. The Permit 
and Conservation Division requested initiation of section 7 
consultation with the Alaska Region for the promulgation of 5-year 
regulations and the subsequent issuance of annual LOAs. The Alaska 
Region issued a Biological Opinion concluding that NMFS' action is not 
likely to adversely affect the listed species named above or adversely 
modify their critical habitat.

Classification

    Pursuant to the procedures established to implement Executive Order 
12866, the Office of Management and Budget has determined that this 
rule is not significant.
    Pursuant to section 605(b) of the Regulatory Flexibility Act (RFA), 
the Chief Counsel for Regulation of the Department of Commerce has 
certified to the Chief Counsel for Advocacy of the Small Business 
Administration that this rule will not have a significant economic 
impact on a substantial number of small entities. Hilcorp Alaska LLC is 
the only entity that is subject to the requirements in these 
regulations. Hilcorp employs thousands of people worldwide, and has a 
market value in the billions of dollars. Therefore, Hilcorp is not a 
small governmental jurisdiction, small organization, or small business, 
as defined by the RFA. Because of this certification, a regulatory 
flexibility analysis is not required and none has been prepared.
    Notwithstanding any other provision of law, no person is required 
to respond to nor shall a person be subject to a penalty for failure to 
comply with a collection of information subject to the requirements of 
the Paperwork Reduction Act (PRA) unless that collection of information 
displays a currently valid OMB control number. This rule contains 
collection-of-information requirements subject to the provisions of the 
PRA. These requirements have been approved by OMB under control number 
0648-0151 and include applications for regulations, subsequent LOAs, 
and reports.

Waiver of Delay in Effective Date

    The Assistant Administrator for NMFS has determined that there is 
good cause under the Administrative Procedure Act (5 U.S.C 553(d)(3)) 
to waive the 30-day delay in the effective date of this final rule. No 
individual or entity other than Hilcorp is affected by the provisions 
of these regulations. Hilcorp has informed NMFS that it requests that 
this final rule take effect as soon as is possible so as to avoid the 
potential for disruption in Hilcorp's planned activities. NMFS was 
unable to accommodate the 30-day delay of effectiveness period due to 
the need for additional time to address public comment and carry out 
required review, which was delayed by the lapse in federal 
appropriations in December 2018 and January 2019. The waiver of the 30-
day delay of the effective date of the final rule will ensure that the 
MMPA final rule and LOA are finalized as soon as is possible to avoid 
the potential for disruption in the Hilcorp's planned activities. In 
addition, the LOA allows for authorization of incidental take of marine 
mammals that would otherwise be prohibited under the statute. Therefore 
the rule is also granting an exception to Hilcorp and relieving 
restrictions under the MMPA. For these reasons, NMFS finds good cause 
to waive the 30-day delay in the effective date.

List of Subjects in 50 CFR Part 217

    Penalties, Reporting and recordkeeping requirements, Seafood, 
Transportation.

    Dated: July 22, 2019.
Samuel D. Rauch III,
Deputy Assistant Administrator for Regulatory Programs, National Marine 
Fisheries Service.

    For reasons set forth in the preamble, 50 CFR part 217 is amended 
as follows:

PART 217--REGULATIONS GOVERNING THE TAKING AND IMPORTING OF MARINE 
MAMMALS

0
1. The authority citation for part 217 continues to read as follows:

    Authority:  16 U.S.C. 1361 et seq.


0
2. Add subpart Q to part 217 to read as follows:
Subpart Q--Taking and Importing Marine Mammals; Taking Marine Mammals 
Incidental to Oil and Gas Activities in Cook Inlet, Alaska.
Sec.
217.160 Specified activity and specified geographical region.
217.161 Effective dates.
217.162 Permissible methods of taking.
217.163 Prohibitions.
217.164 Mitigation requirements.
217.165 Requirements for monitoring and reporting.
217.166 Letters of Authorization.
217.167 Renewals and modifications of Letters of Authorization and 
adaptive management.
217.168-217.169 [Reserved]

Subpart Q--Taking and Importing Marine Mammals; Taking Marine 
Mammals Incidental to Oil and Gas Activities in Cook Inlet, Alaska.


Sec.  217.160   Specified activity and specified geographical region.

    (a) Regulations in this subpart apply only to Hilcorp Alaska LLC 
(Hilcorp)

[[Page 37503]]

and those persons it authorizes or funds to conduct activities on its 
behalf for the taking of marine mammals that occurs in the area 
outlined in paragraph (b) of this section and that occurs incidental to 
the activities described in paragraph (c) of this section.
    (b) The taking of marine mammals by Hilcorp may be authorized in 
Letters of Authorization (LOAs) only if it occurs within the action 
area defined in Cook Inlet, Alaska.
    (c) The taking of marine mammals by Hilcorp is only authorized if 
it occurs incidental to Hilcorp's oil and gas activities including use 
of seismic airguns, sub-bottom profiler, vertical seismic profiling, 
pile driving, conductor pipe driving, and water jets.


Sec.  217.161   Effective dates.

    Regulations in this subpart are effective July 30, 2019, through 
July 30, 2024.


Sec.  217.162   Permissible methods of taking.

    Under LOAs issued pursuant to Sec. Sec.  216.106 of this chapter 
and 217.166, the Holder of the LOAs (hereinafter ``Hilcorp'') may 
incidentally, but not intentionally, take marine mammals within the 
area described in Sec.  217.160(b) by Level A harassment and Level B 
harassment associated with oil and gas activities, provided the 
activity is in compliance with all terms, conditions, and requirements 
of the regulations in this subpart and the applicable LOAs.


Sec.  217.163   Prohibitions.

    Notwithstanding takings contemplated in Sec.  217.162 and 
authorized by LOAs issued under Sec. Sec.  216.106 of this chapter and 
217.166, no person in connection with the activities described in Sec.  
217.160 may:
    (a) Violate, or fail to comply with, the terms, conditions, and 
requirements of this subpart or a LOA issued under Sec. Sec.  216.106 
of this chapter and 217.166;
    (b) Take any marine mammal not specified in such LOAs;
    (c) Take any marine mammal specified in such LOAs in any manner 
other than as specified;
    (d) Take a marine mammal specified in such LOAs if NMFS determines 
such taking results in more than a negligible impact on the species or 
stocks of such marine mammal; or
    (e) Take a marine mammal specified in such LOAs if NMFS determines 
such taking results in an unmitigable adverse impact on the 
availability of such species or stock of marine mammal for taking for 
subsistence uses.


Sec.  217.164   Mitigation requirements.

    When conducting the activities identified in Sec.  217.160(c), the 
mitigation measures contained in any LOAs issued under Sec. Sec.  
216.106 of this chapter and 217.166 must be implemented. These 
mitigation measures must include but are not limited to:
    (a) Hilcorp must conduct a sound source verification (SSV) for 3D 
seismic and sub-bottom profiler use. Results of this SSV must be sent 
to NMFS and mitigation and monitoring zones may be adjusted based on 
the results of the SSV.
    (b) If any marine mammal species for which take is not authorized 
are sighted within or entering the relevant zones within which they are 
be exposed to sound above the 120 dB re 1 [micro]Pa (rms) threshold for 
continuous (e.g., vibratory pile-driving, drilling) sources or the 160 
dB re 1 [micro]Pa (rms) threshold for non-explosive impulsive (e.g., 
seismic airguns) or intermittent (e.g., scientific sonar) sources, 
Hilcorp must take appropriate action to avoid such exposure (e.g., by 
altering speed or course or by shutdown of the sound source).
    (c) If the allowable number of takes in an LOA listed for any 
marine mammal species is met or exceeded, Hilcorp must immediately 
cease survey operations involving the use of active sound source(s), 
record the observation, and notify NMFS Office of Protected Resources.
    (d) Hilcorp must notify NMFS Office of Protected Resources at least 
48 hours prior to the start of oil and gas activities each year.
    (e) Hilcorp must conduct briefings as necessary between vessel 
crews, marine mammal monitoring team, and other relevant personnel 
prior to the start of all survey activity, and when new personnel join 
the work, in order to explain responsibilities, communication 
procedures, marine mammal monitoring protocol, and operational 
procedures.
    (f) Hilcorp must establish monitoring and exclusion zones.
    (1) For all relevant in-water activity, Hilcorp must implement 
shutdown zones/exclusion zones (EZs) with radial distances as 
identified in any LOA issued under Sec. Sec.  216.106 of this chapter 
and 217.166. If a marine mammal is sighted within or entering the EZ, 
such operations must cease.
    (2) For all relevant in-water activity, Hilcorp must designate 
safety zones for monitoring (SZ) with radial distances as identified in 
any LOA issued under Sec. Sec.  216.106 of this chapter and 217.166 and 
record and report occurrence of marine mammals within these zones.
    (3) For all relevant in-water activity, Hilcorp must implement a 
minimum EZ of a 10 m radius around the source.
    (g) Hilcorp must implement shutdown measures.
    (1) Hilcorp must deploy protected species observers (PSO) and PSOs 
must be posted to monitor marine mammals within the monitoring zones 
during use of active acoustic sources and pile driving in water.
    (2) Monitoring must begin 15 minutes prior to initiation of 
stationary source activity and 30 minutes prior to initiation of mobile 
source activity, occur throughout the time required to complete the 
activity, and continue through 30 minutes post-completion of the 
activity. Pre-activity monitoring must be conducted to ensure that the 
EZ is clear of marine mammals, and activities may only commence once 
observers have declared the EZ clear of marine mammals. In the event of 
a delay or shutdown of activity resulting from marine mammals in the 
EZ, the marine mammals' behavior must be monitored and documented.
    (3) A determination that the EZ is clear must be made during a 
period of good visibility (i.e., the entire EZ must be visible to the 
naked eye).
    (4) If a marine mammal is observed within or entering the EZ, 
Hilcorp must halt all noise producing activities for which take is 
authorized at that location. If activity is delayed due to the presence 
of a marine mammal, the activity may not commence or resume until 
either the animal has voluntarily left and been visually confirmed 
outside the EZ or the required amount of time (15 for porpoises and 
pinnipeds, 30 minutes for cetaceans) have passed without re-detection 
of the animal.
    (5) Monitoring must be conducted by trained observers, who must 
have no other assigned tasks during monitoring periods. Trained 
observers must be placed at the best vantage point(s) practicable to 
monitor for marine mammals and implement shutdown or delay procedures 
when applicable through communication with the equipment operator. 
Hilcorp must adhere to the following additional observer 
qualifications:
    (i) Hilcorp must use independent, dedicated, trained visual PSOs, 
meaning that the PSOs must be employed by a third-party observer 
provider, must not have tasks other than to conduct observational 
effort, collect data, and communicate with and instruct relevant vessel 
crew with regard to the presence of protected species and mitigation 
requirements (including brief alerts regarding maritime hazards), and 
must have successfully completed an

[[Page 37504]]

approved PSO training course appropriate for their designated task.
    (ii) Hilcorp must submit PSO resumes for NMFS review and approval. 
Resumes must be accompanied by a relevant training course information 
packet that includes the name and qualifications (i.e., experience, 
training completed, or educational background) of the instructor(s), 
the course outline or syllabus, and course reference material as well 
as a document stating successful completion of the course. NMFS will 
approve or disapprove PSOs within one week from the time that the 
necessary information is received by NMFS, after which PSOs meeting the 
minimum requirements will automatically be considered approved.
    (iii) To the maximum extent practicable, the lead PSO must devise 
the duty schedule such that experienced PSOs are on duty with those 
PSOs with appropriate training but who have not yet gained relevant 
experience.
    (6) Operations must shut down completely if a beluga whale is 
sighted within the relevant Level B harassment isopleth.
    (h) Hilcorp must implement soft start techniques for impact pile 
driving.
    (1) Hilcorp must conduct an initial set of three strikes from the 
impact hammer 30 seconds apart, at 40 percent energy, followed by a 1-
minute waiting period, then two subsequent three strike sets.
    (2) Soft start is required for any impact driving, including at the 
beginning of the day, after 30 minutes of pre-activity monitoring, and 
at any time following a cessation of impact pile driving of 30 minutes 
or longer.
    (i) Hilcorp must implement ramp ups for seismic airgun use.
    (1) Ramp up must be used at the start of airgun operations, 
including after a shutdown, and after any period greater than 30 
minutes in duration without airgun operations.
    (2) The rate of ramp up must be no more than 6 dB per 5-minute 
period.
    (3) Ramp up must begin with the smallest gun in the array that is 
being used for all airgun array configurations.
    (4) During the ramp up, the EZ for the full airgun array must be 
implemented.
    (5) If the complete EZ has not been visible for at least 30 minutes 
prior to the start of operations, ramp up must not commence.
    (6) Ramp up of the airguns must not be initiated if a marine mammal 
is sighted within or entering the EZ at any time.
    (j) Hilcorp must use aircraft for mitigation.
    (1) Hilcorp must use aircraft daily to survey the planned seismic 
survey area prior to the start of seismic surveying. Surveying must not 
begin unless the aerial flights confirm the planned survey area for 
that day is clear of beluga whales. If weather conditions make flying 
before the start of seismic in daylight unsafe, Hilcorp may delay the 
aerial survey until weather conditions improve and it is safe to fly.
    (2) If beluga whales are sighted during flights, start of seismic 
surveying must be delayed until it is confirmed the area is free of 
beluga whales.
    (k) Hilcorp must implement exclusion zones for beluga whales.
    (1) Hilcorp must not operate with noise producing activity within 
10 miles (16 km) of the mean higher high water (MHHW) line of the 
Susitna Delta (Beluga River to the Little Susitna River) between April 
15 and October 15. Hilcorp must not conduct seismic activity within the 
Level B isopleth distance of the mouth of the Kasilof River between 
January 1 and May 31.
    (m) Hilcorp must abide by all mitigation measures described in the 
Biological Opinion for Hilcorp Alaska and Harvest Alaska Oil and Gas 
Activities, Cook Inlet, Alaska.


Sec.  217.165   Requirements for monitoring and reporting.

    (a) Marine mammal monitoring protocols. Hilcorp must conduct 
briefings between construction supervisors and crews and the observer 
team prior to the start of all pile driving and removal activities, and 
when new personnel join the work. Trained observers must receive a 
general environmental awareness briefing conducted by Hilcorp staff. At 
minimum, training must include identification of marine mammals that 
may occur in the project vicinity and relevant mitigation and 
monitoring requirements. All observers must have no other construction-
related tasks while conducting monitoring.
    (b) Visibility. Activities must only commence when the entire 
exclusion zone (EZ) is visible to the naked eye and can be adequately 
monitored. If conditions (e.g., fog) prevent the visual detection of 
marine mammals, activities must not be initiated. For activities other 
than seismic surveying, activity must be halted in low visibility but 
vibratory pile driving or removal will be allowed to continue if 
started in good visibility.
    (c) Monitoring periods. Monitoring must begin 15 minutes prior to 
initiation of stationary source activity and 30 minutes prior to 
initiation of mobile source activity, occur throughout the time 
required to complete the activity, and continue through 30 minutes 
post-completion of the activity. Pre-activity monitoring must be 
conducted to ensure that the EZ is clear of marine mammals, and 
activities may only commence once observers have declared the EZ clear 
of marine mammals. In the event of a delay or shutdown of activity 
resulting from marine mammals in the EZ, the animals' behavior must be 
monitored and documented.
    (d) Placement of PSOs. (1) At least one on-duty PSO must be placed 
on the source vessel (for seismic and geohazard surveys) or drill rig 
(for pipe driving and VSP).
    (2) During seismic surveys a mitigation vessel must be used with at 
least one on-duty PSO aboard the vessel monitoring for marine mammal 
occurrence.
    (e) Reporting measures--(1) Take limits. Hilcorp must contact NMFS 
when they have reached the limit of authorized takes of beluga whale 
within a year.
    (2) Monthly reports. Monthly reports must be submitted to NMFS for 
all months during which in-water seismic activities take place. The 
monthly report must contain and summarize the following information: 
Dates, times, locations, heading, speed, weather, sea conditions 
(including Beaufort sea state and wind force), and associated 
activities during all seismic operations and marine mammal sightings; 
Species, number, location, distance from the vessel, and behavior of 
any sighted marine mammals, as well as associated seismic activity 
(number of power-downs and shutdowns), observed throughout all 
monitoring activities; An estimate of the number (by species) exposed 
to the seismic activity (based on visual observation) at received 
levels greater than or equal to the NMFS thresholds discussed above 
with a discussion of any specific behaviors those individuals 
exhibited; A description of the implementation and effectiveness of the 
terms and conditions of the Biological Opinion's Incidental Take 
Statement (ITS) and mitigation measures of the LOA.
    (3) Annual reports. (i) Hilcorp must submit an annual report within 
90 days after each activity year, starting from the date when the LOA 
is issued (for the first annual report) or from the date when the 
previous annual report ended.
    (ii) Annual reports will detail the monitoring protocol, summarize 
the data recorded during monitoring, and estimate the number of marine 
mammals that may have been harassed during the period of the report.
    (iii) NMFS will provide comments within 30 days after receiving 
annual reports, and Hilcorp must address the

[[Page 37505]]

comments and submit revisions within 30 days after receiving NMFS 
comments. If no comment is received from the NMFS within 30 days, the 
annual report will be considered completed.
    (4) Final report. (i) Hilcorp must submit a comprehensive summary 
report to NMFS not later than 90 days following the conclusion of 
marine mammal monitoring efforts described in this subpart.
    (ii) The final report must synthesize all data recorded during 
marine mammal monitoring, and estimate the number of marine mammals 
that may have been harassed through the entire project.
    (iii) NMFS will provide comments within 30 days after receiving 
this report, and Hilcorp must address the comments and submit revisions 
within 30 days after receiving NMFS comments. If no comment is received 
from the NMFS within 30 days, the final report will be considered as 
final.
    (5) Reporting of injured or dead marine mammals. (i) In the event 
that personnel involved in the survey activities discover an injured or 
dead marine mammal, Hilcorp must report the incident to the Office of 
Protected Resources (OPR), NMFS (301-427-8401) and to regional 
stranding network (877- 925-7773) as soon as feasible. The report must 
include the following information:
    (A) Time, date, and location (latitude/longitude) of the first 
discovery (and updated location information if known and applicable);
    (B) Species identification (if known) or description of the 
animal(s) involved;
    (C) Condition of the animal(s) (including carcass condition if the 
animal is dead);
    (D) Observed behaviors of the animal(s), if alive;
    (E) If available, photographs or video footage of the animal(s); 
and
    (F) General circumstances under which the animal was discovered.
    (ii) In the event of a ship strike of a marine mammal by any vessel 
involved in the survey activities, Hilcorp must report the incident to 
OPR, NMFS and to regional stranding networks as soon as feasible. The 
report must include the following information:
    (A) Time, date, and location (latitude/longitude) of the incident;
    (B) Species identification (if known) or description of the 
animal(s) involved;
    (C) Vessel's speed during and leading up to the incident;
    (D) Vessel's course/heading and what operations were being 
conducted (if applicable);
    (E) Status of all sound sources in use;
    (F) Description of avoidance measures/requirements that were in 
place at the time of the strike and what additional measures were 
taken, if any, to avoid strike;
    (G) Environmental conditions (e.g., wind speed and direction, 
Beaufort sea state, cloud cover, visibility) immediately preceding the 
strike;
    (H) Estimated size and length of animal that was struck;
    (I) Description of the behavior of the marine mammal immediately 
preceding and following the strike;
    (J) If available, description of the presence and behavior of any 
other marine mammals immediately preceding the strike;
    (K) Estimated fate of the animal (e.g., dead, injured but alive, 
injured and moving, blood or tissue observed in the water, status 
unknown, disappeared); and
    (L) To the extent practicable, photographs or video footage of the 
animal(s).
    (iii) In the event of a live stranding (or near-shore atypical 
milling) event within 50 km of the survey operations, where the NMFS 
stranding network is engaged in herding or other interventions to 
return animals to the water, the Director of OPR, NMFS (or designee) 
will advise Hilcorp of the need to implement shutdown procedures for 
all active acoustic sources operating within 50 km of the stranding. 
Shutdown procedures for live stranding or milling marine mammals 
include the following:
    (A) If at any time, the marine mammal(s) die or are euthanized, or 
if herding/intervention efforts are stopped, the Director of OPR, NMFS 
(or designee) will advise Hilcorp that the shutdown around the animals' 
location is no longer needed.
    (B) Otherwise, shutdown procedures must remain in effect until the 
Director of OPR, NMFS (or designee) determines and advises Hilcorp that 
all live animals involved have left the area (either of their own 
volition or following an intervention).
    (C) If further observations of the marine mammals indicate the 
potential for re-stranding, additional coordination with Hilcorp must 
occur to determine what measures are necessary to minimize that 
likelihood (e.g., extending the shutdown or moving operations farther 
away) and Hilcorp must implement those measures as appropriate.
    (iv) If NMFS determines that the circumstances of any marine mammal 
stranding found in the vicinity of the activity suggest investigation 
of the association with survey activities is warranted, and an 
investigation into the stranding is being pursued, NMFS will submit a 
written request to Hilcorp indicating that the following initial 
available information must be provided as soon as possible, but no 
later than 7 business days after the request for information.
    (A) Status of all sound source use in the 48 hours preceding the 
estimated time of stranding and within 50 km of the discovery/
notification of the stranding by NMFS; and
    (B) If available, description of the behavior of any marine 
mammal(s) observed preceding (i.e., within 48 hours and 50 km) and 
immediately after the discovery of the stranding.
    (C) In the event that the investigation is still inconclusive, the 
investigation of the association of the survey activities is still 
warranted, and the investigation is still being pursued, NMFS may 
provide additional information requests, in writing, regarding the 
nature and location of survey operations prior to the time period 
above.


Sec.  217.166   Letters of Authorization.

    (a) To incidentally take marine mammals pursuant to these 
regulations, Hilcorp must apply for and obtain (LOAs) in accordance 
with Sec.  216.106 of this chapter for conducting the activity 
identified in Sec.  217.160(c).
    (b) LOAs, unless suspended or revoked, may be effective for a 
period of time not to extend beyond the expiration date of these 
regulations.
    (c) An LOA application must be submitted to the Director, Office of 
Protected Resources, NMFS, by March 1st of the year preceding the 
desired start date.
    (d) An LOA application must include the following information:
    (1) \The date(s), duration, and the area(s) where the activity will 
occur;
    (2) The species and/or stock(s) of marine mammals likely to be 
found within each area;
    (3) The estimated number of takes for each marine mammal stock 
potentially affected in each area for the period of effectiveness of 
the Letter of Authorization.
    (4) An updated Stakeholder Engagement Plan detailing Hilcorp's 
meetings with stakeholders and any concerns raised that relate to 
marine mammals or subsistence activities.
    (e) In the event of projected changes to the activity or to 
mitigation, monitoring, reporting (excluding changes made pursuant to 
the adaptive management provision of Sec.  217.97(c)(1)) required by an 
LOA, Hilcorp must apply for and obtain a modification of LOAs as 
described in Sec.  217.167.

[[Page 37506]]

    (f) Each LOA must set forth:
    (1) Permissible methods of incidental taking;
    (2) Means of effecting the least practicable adverse impact (i.e., 
mitigation) on the species, their habitat, and the availability of the 
species for subsistence uses; and
    (3) Requirements for monitoring and reporting.
    (g) Issuance of the LOA(s) must be based on a determination that 
the level of taking must be consistent with the findings made for the 
total taking allowable under these regulations.
    (h) If NMFS determines that the level of taking is resulting or may 
result in more than a negligible impact on the species or stocks of 
such marine mammal, the LOA may be modified or suspended after notice 
and a public comment period.
    (i) Notice of issuance or denial of the LOA(s) must be published in 
the Federal Register within 30 days of a determination.


Sec.  217.167   Renewals and modifications of Letters of Authorization 
and adaptive management.

    (a) An LOA issued under Sec. Sec.  216.106 of this chapter and 
217.166 for the activity identified in Sec.  217.160(c) may be renewed 
or modified upon request by the applicant, provided that the following 
are met:
    (1) Notification to NMFS that the activity described in the 
application submitted under Sec.  217.160(a) will be undertaken and 
that there will not be a substantial modification to the described 
work, mitigation or monitoring undertaken during the upcoming or 
remaining LOA period;
    (2) Timely receipt (by the dates indicated) of monitoring reports, 
as required under Sec.  217.165(C)(3);
    (3) A determination by the NMFS that the mitigation, monitoring and 
reporting measures required under Sec.  217.165(c) and the LOA issued 
under Sec. Sec.  216.106 of this chapter and 217.166, were undertaken 
and are expected to be undertaken during the period of validity of the 
LOA.
    (b) If a request for a renewal of a Letter of Authorization 
indicates that a substantial modification, as determined by NMFS, to 
the described work, mitigation or monitoring undertaken during the 
upcoming season will occur, NMFS will provide the public a period of 30 
days for review and comment on the request as well as the proposed 
modification to the LOA. Review and comment on renewals of Letters of 
Authorization are restricted to:
    (1) New cited information and data indicating that the original 
determinations made for the regulations are in need of reconsideration; 
and
    (2) Proposed changes to the mitigation and monitoring requirements 
contained in these regulations or in the current Letter of 
Authorization.
    (c) A notice of issuance or denial of a renewal of a Letter of 
Authorization will be published in the Federal Register within 30 days 
of a determination.
    (d) An LOA issued under Sec. Sec.  216.16 of this chapter and 
217.166 for the activity identified in Sec.  217.160 may be modified by 
NMFS under the following circumstances:
    (1) Adaptive management. NMFS, in response to new information and 
in consultation with Hilcorp, may modify the mitigation or monitoring 
measures in subsequent LOAs if doing so creates a reasonable likelihood 
of more effectively accomplishing the goals of mitigation and 
monitoring set forth in the preamble of these regulations.
    (i) Possible sources of new data that could contribute to the 
decision to modify the mitigation or monitoring measures include:
    (A) Results from Hilcorp's monitoring from the previous year(s).
    (B) Results from marine mammal and/or sound research or studies.
    (C) Any information that reveals marine mammals may have been taken 
in a manner, extent or number not authorized by these regulations or 
subsequent LOAs.
    (ii) If, through adaptive management, the modifications to the 
mitigation, monitoring, or reporting measures are substantial, NMFS 
will publish a notice of proposed LOA in the Federal Register and 
solicit public comment.
    (2) Withdrawal or suspension. NMFS will withdraw or suspend an LOA 
if, after notice and opportunity for public comment, NMFS determines 
these regulations are not being substantially complied with or that the 
taking allowed is or may be having more than a negligible impact on an 
affected species or stock specified in Sec.  217.162(b) or an 
unmitigable adverse impact on the availability of the species or stock 
for subsistence uses. The requirement for notice and comment will not 
apply if NMFS determines that an emergency exists that poses a 
significant risk to the well-being of the species or stocks of marine 
mammals. Notice will be published in the Federal Register within 30 
days of such action.


Sec. Sec.  217.168--217.169   [Reserved]

[FR Doc. 2019-15867 Filed 7-30-19; 8:45 am]
 BILLING CODE 3510-22-P