Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Construction and Operation of the Liberty Drilling and Production Island, Beaufort Sea, Alaska
Federal RegisterMay 29, 2019
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
50 CFR Part 217
[Docket No. 180627584-9388-01]
RIN 0648-BI00
Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Construction and Operation of the Liberty Drilling and Production Island, Beaufort Sea, Alaska
AGENCY:
National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.
ACTION:
Proposed rule; request for comments.
SUMMARY:
NMFS has received a request from Hilcorp Alaska (Hilcorp) for authorization to take marine mammals incidental to construction and operation of the Liberty Drilling and Production Island (LDPI), over the course of five years. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is proposing regulations to govern that take, and requests comments on the proposed regulations. NMFS will consider public comments prior to making any final decision on the issuance of the requested MMPA authorization and agency responses will be summarized in the final notice of our decision.
DATES:
Comments and information must be received no later than June 28, 2019.
ADDRESSES:
You may submit comments on this document, identified by NOAA-NMFS-2018-0053, by any of the following methods:
•
Electronic submission:
Submit all electronic public comments via the Federal e-Rulemaking Portal. Go to
www.regulations.gov/#!docketDetail;D=NOAA-NMFS-2019-0053
click the “Comment Now!” icon, complete the required fields, and enter or attach your comments.
•
Mail:
Submit written comments to Jolie Harrison, Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East West Highway, Silver Spring, MD 20910.
Instructions:
Comments sent by any other method, to any other address or individual, or received after the end of the comment period, may not be considered by NMFS. All comments received are a part of the public record and will generally be posted for public viewing on
www.regulations.gov
without change. All personal identifying information (
e.g.,
name, address), confidential business information, or otherwise sensitive information submitted voluntarily by the sender will be publicly accessible. NMFS will accept anonymous comments (enter “N/A” in the required fields if you wish to remain anonymous). Attachments to electronic comments will be accepted in Microsoft Word, Excel, or Adobe PDF file formats only.
FOR FURTHER INFORMATION CONTACT:
Jaclyn Daly, 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
https://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
NMFS received an application from Hilcorp requesting five-year regulations and authorization to incidentally take multiple species of marine mammals in Foggy Island Bay, Beaufort Sea, by Level A harassment (non-serious injury) and Level B harassment (behavioral disturbance), incidental to construction and operation of the LDPI and associated infrastructure. Please see “Background” below for definitions of harassment. In addition, a limited unintentional take involving the mortality or serious injury of no more than two ringed seals (
Phoca hispida
) would be authorized to occur during annual ice road construction and maintenance. This proposed rule establishes 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 activities related to construction and operation of the LDPI.
Legal Authority for the Proposed Action
Section 101(a)(5)(A) of the MMPA (16 U.S.C. 1371(a)(5)(A)) directs the Secretary of Commerce to allow, upon request, the incidental, but not intentional taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region for up to 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 “Proposed Mitigation” section), as well as monitoring and reporting requirements. Section 101(a)(5)(A) of the MMPA and the implementing regulations at 50 CFR part 216, subpart I provide the legal basis for issuing this proposed rule containing five-year regulations, and for any subsequent Letters of Authorization (LOAs). As directed by this legal authority, this proposed rule contains mitigation, monitoring, and reporting requirements.
Summary of Major Provisions Within the Proposed Rule
Following is a summary of the major provisions of this proposed rule Hilcorp would be required to implement. These measures include:
• Use of soft start during impact pile driving to allow marine mammals the opportunity to leave the area prior to beginning impact pile driving at full power;
• Implementation of shutdowns of construction activities under certain circumstances to minimize harassment, including injury;
• Prohibition on impact pile driving during the fall Cross Island bowhead whale hunt and seasonal drilling restrictions to minimize impacts to marine mammals and subsistence users;
• Implementation of best management practices to avoid and minimize ice seal and habitat disturbance during ice road construction, maintenance, and use;
• Use of marine mammal and acoustic monitoring to detect marine mammals and verify predicted sound fields;
• Coordination with subsistence users and adherence to a Plan of Cooperation (POC); and
• Limitation on vessel speeds and transit areas, where appropriate.
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 is provided to the public for review. Under the MMPA, “take” is defined as meaning to harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or kill any marine mammal. “Harassment” is statutorily defined as any act of pursuit, torment, or annoyance which has the potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment) or 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 but which does not have the potential to injure a marine mammal or marine mammal stock in the wild (Level B harassment).
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 are set forth.
National Environmental Policy Act
To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321
et seq.
) and NOAA Administrative Order (NAO) 216-6A, NMFS must evaluate our proposed action (
i.e.,
the promulgation of regulations and subsequent issuance of incidental take authorization) and alternatives with respect to potential impacts on the human environment.
On August 23, 2018, the Bureau of Ocean Energy Management (BOEM) released a Final Environmental Impact Statement (EIS) analyzing the possible environmental impacts of Hilcorp's proposed Liberty development and production plan (DPP). BOEM's Draft EIS was made available for public comment from August 18, 2017 through December 8, 2017. The final EIS may be found at
https://www.boem.gov/hilcorp-liberty/.
NMFS is a cooperating agency on the EIS. Accordingly, NMFS plans to adopt the EIS, provided our independent evaluation of the document finds that it includes adequate information analyzing the effects on the human environment of issuing the rule. We will review all comments submitted in response to this notice prior to concluding our NEPA process or making a final decision on the regulations request.
Summary of Request
On August 2, 2017, Hilcorp petitioned NMFS for rulemaking under Section 101(a)(5)(A) of the MMPA to authorize the take of six species of marine mammals incidental to construction and operation of the proposed LDPI in Foggy Island Bay, Alaska. On April 26, 2018, Hilcorp submitted a revised petition which NMFS deemed adequate and complete. On May 9, 2018, we published a notice of receipt of Hilcorp's petition in the
Federal Register
, requesting comments and information related to the request for thirty days (83 FR 21276). We received comments from the Center for Biological Diversity and 15,843 citizens opposing issuance of the requested regulations and LOA. We also received comments from the Alaska Eskimo Whaling Commission (AEWC) who recommended we include subsistence related mitigation and coordination requirements in the final rule. The comments and information received were considered in development of this proposed rule and are available online at
https://www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-mammal-protection-act.
More recently, Hilcorp provided subsequent additional information, including details on a previously undescribed component of the project (installation of foundation piles in the interior of the LDPI), and revised marine mammal density and estimate take numbers on February 4, 2019. Hilcorp also updated their proposed Marine Mammal Mitigation and Monitoring Plan (4MP) on January 29, 2019.
To extract oil and gas in the Liberty Oil Field, Hilcorp is proposing to construct a 9.3 acre artificial island (the LDPI) in 19 feet (ft) (5.8 meters (m)) of water in Foggy Island Bay, approximately 5 miles (mi) (8 kilometers (km)) north of the Kadleroshilik River and install supporting infrastructure (
e.g.,
ice roads, pipeline). Ice roads would be constructed annually and begin December 2020. Island construction, which requires impact and vibratory pile driving, is proposed to commence and be completed in 2021. Pile driving would primarily occur during ice-covered season (only ice seals are present during this time period); however, up to two weeks of pile driving may occur during the open-water season. Pipeline installation is anticipated to occur in 2022. Drilling and production is proposed to occur from 2022 through 2025.
Hilcorp requests, and NMFS is proposing to authorize, the take, by Level A harassment and Level B harassment, of bowhead whales (
Balaena mysticetus
), gray whales (
Eschrichtius robustus),
beluga whales (
Delphinapterus leucas
), ringed seals (
Phoca hispida
), bearded seals (
Erignathus barbatus
), and spotted seals (
Phoca largha
) incidental to LDPI construction and operation activities (
e.g.,
pile driving, ice road and island construction). Hilcorp also requested, and NMFS is proposing to authorize, mortality and serious injury of two ringed seals incidental to annual ice road construction over a 5-year period. The proposed regulations and LOA would be valid for five years from December 1, 2020, through November 30, 2025.
Description of the Specified Activity
Overview
Hilcorp is proposing to construct and operate the LDPI, a self-contained offshore drilling and production facility located on an artificial gravel island. Infrastructure and facilities necessary to drill wells and process and export approximately 60,000 to 70,000 barrels of oil per day to shore would be installed on the island. To transport oil, a pipeline from the island would be installed, tying into the existing Bandami pipeline located on shore between the Sagavanirktok and Kadleroshilik Rivers on Alaska's North Slope. To access the island and move vehicles and equipment, ice roads would be constructed annually. All island construction and pipeline installation would occur during winter months as much as possible; however, pile driving and slope protection could occur during the open water season. Drilling and production, once begun, would occur year round. After island and pipeline construction, Hilcorp would commence and continue drilling and production for approximately 20 to 25 years at which time the island would be decommissioned. The proposed regulations and LOA would cover the incidental take of marine mammals during LDPI construction and operation for the first five years of work. Thereafter, data collected during these five years (
e.g.,
acoustic monitoring during drilling, ice road marine mammal monitoring) would determine
if future incidental take authorizations are warranted for continuing operations.
Dates and Duration
The proposed regulations would be valid for a period of five years from December 1, 2020, through November 30, 2025. Ice road construction and pipeline installation would be limited to winter months. Island construction would be conducted primarily during winter months; however, given construction schedules are subject to delays for multiple reasons. Hilcorp anticipates, at most, up to two weeks of open-water pile driving may be required in the first year to complete any pile driving not finished during the winter. Other work such as island slope armoring may also occur during open-water conditions. All island construction would commence and is expected to be completed in the first year of the proposed regulations (December 2020 through November 2021). Pipeline installation would occur in year 2 of the proposed regulations (December 2021 through November 2022), while drilling and production would begin in year 3 and continue through the life of the proposed regulations. Ice road construction and maintenance activities would occur each winter.
Specified Geographical Region
The Liberty field is located in Federal waters of Foggy Island Bay, Beaufort Sea about 8.9 km (5.5 mi) offshore in 6.1 m (20 ft) of water and approximately 8 to 13 km (5 to 8 mi) east of the existing Endicott Satellite Drilling Island (SDI) and approximately 32 km (20 mi) east of Prudhoe Bay. Hilcorp would construct the Liberty project on three leases, OCS-Y-1650, OCS-Y-1886, and OCS-Y-1585. The proposed LDPI would be constructed in 19 ft (5.8 m) of water about 5 mi (8 km) offshore in Foggy Island Bay. The LDPI and all associated infrastructure (
e.g.,
ice roads) are located inside the McClure barrier island group which separates Foggy Island Bay from the Beaufort Sea (Figure 1).
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Detailed Description of Activities
The Liberty Prospect is located 8.85 km offshore in about 6 m of water, inside the Beaufort Sea's barrier islands. Hilcorp, as the Liberty operator, is proposing to develop the Liberty Oil Field reservoir, located on the Outer Continental Shelf (OCS), in Foggy Island Bay, Beaufort Sea, Alaska. The Liberty reservoir is the largest delineated but undeveloped light oil reservoir on the North Slope. It is projected to deliver a peak production rate of between 60,000 and 70,000 barrels of oil per day within two years of initial production. Total recovery over an estimated field life of 15 to 20 years is predicted to be in the range of 80 to 150 million stock tank barrels of oil. The Liberty Oil Field leases were previously owned by BP Exploration Alaska, Inc. (BPXA). In April 2014, BPXA announced the sale of several North Slope assets to Hilcorp including the area where the proposed LDPI would be constructed and other existing oil production islands (Northstar, Endicott, Milne Point). The Liberty Project has many similarities to previous oil and gas islands constructed on the North Slope, including Endicott, Northstar and Oooguruk.
The proposed LDPI project includes development of a mine-site to supply gravel for the construction of the LDPI, construction of the island and annual ice roads, installation of an undersea pipeline that reaches shore from the LDPI and then connects to the existing above-ground Badami pipeline, drilling, production and operation (for simplicity, hence forward we refer to both production and operation as “production”). The mine site is located inland of marine mammal habitat over which NMFS has jurisdiction; therefore, its development will not be discussed further in this proposed rule as no impacts to marine mammals under NMFS jurisdiction would be affected by this project component. Here, we discuss those activities that have the potential to take marine mammals: Ice road construction and maintenance, island construction (pile driving and slope armoring), pipeline installation, drilling and production. We also describe auxiliary activities, including vessel and aircraft transportation. A schedule of all phases on the project and summary of equipment and activities involved are included in Table 1.
Table 1—LDPI Project Components, Schedule, and Associated Equipment
Project component
Regulation
year
Season
Equipment and activity
Ice road construction, use, and maintenance
1-5
Ice-covered
Grader, ice auger, trucks (flood road, haul gravel, general transit, maintenance).
Island construction
* 1
Ice-covered, open water
Impact and vibratory pile and pipe driving, backhoe (digging), excavator (slope shaping, armor installation, ditchwitch (sawing ice).
Pipeline installation
2
Ice-covered
Ditchwitch (sawing ice), backhoe (digging), trucks.
Drilling and production
3-5
Ice-covered, open water
Drill rig, land-based equipment on island (
e.g.,
generators).
Marine vessel and aircraft support
1-5
Open-water, ice-covered (helicopter only)
Barge, tugs, crew boats, helicopter.
Emergency and oil response training
1-5
Ice-covered, open water
Vessels, hovercrafts, all-terrain vehicles, snow machines, etc.
* Hilcorp has indicated a goal to complete all LDPI construction in the first year the regulations would be valid; however, they may need to install foundation piles in year 2.
Ice Road and Ice Pad Construction and Maintenance
Hilcorp will construct ice roads and perform maintenance, as necessary. Ice roads are a route across sea ice created by clearing and grading snow then pumping seawater from holes drilled through the floating ice. Some roads may use grounded ice. Hilcorp would clear away snow using a tractor, bulldozer, or similar piece of equipment then pump seawater from holes drilled through floating ice, and then flood the ice road. The ice roads will generally be constructed by pumper units equipped with an ice auger to drill holes in the sea ice and then pump water from under the ice to flood the surface of the ice. The ice augers and pumping units will continue to move along the ice road alignment to flood the entire alignment, returning to a previous area as soon as the flooded water has frozen. The ice road will be maintained and kept clean of gravel and other solids. Freshwater can be sprayed onto the road surface to form a cap over the main road structure for the top layer or to repair any cracks.
Ice roads will be used for onshore and offshore access, installing the pipeline, hauling gravel used to construct the island, moving equipment on/off island, personnel and supply transit, etc. Ice roads are best constructed when weather is -20 degrees Fahrenheit (F) to -30 degrees F, but temperatures below 0 degree F are considered adequate for ice road construction. Ice road construction can typically be initiated in mid- to late-December and roads maintained until mid-May. At the end of the season, ice roads will be barricaded by snow berm and/or slotted at the entrance to prevent access and allowed to melt naturally. Figure 1 shows the locations of the proposed ice roads.
• Ice road # 1 will extend approximately 11.3 km (7 mi) over shorefast sea ice from the Endicott SDI to the LDPI (the SDI to LDPI ice road). It will be approximately 37 m wide (120 ft) with driving lane of approximately 12 m (40 ft). It would cover approximately 160 acres of sea ice.
• Ice road # 2 (approximately 11.3 km (7 mi)) will connect the LDPI to the proposed Kadleroshilik River gravel mine site and then will continue to the juncture with the Badami ice road (which is ice road # 4). It will be approximately 15 m (50 ft) wide.
• Ice road # 3 (approximately 9.6 km [6 mi], termed the “Midpoint Access Road”) will intersect the SDI to LDPI ice road and the ice road between the LDPI and the mine site. It will be approximately 12 m (40 ft) wide.
• Ice road # 4 (approximately 19.3 km (12 mi)), located completely onshore, will parallel the Badami pipeline and connect the mine site with the Endicott road.
All four ice roads would be constructed for the first three years to support pipeline installation and transportation from existing North Slope roads to the proposed gravel mine site, and from the mine site to the proposed LDPI location in the Beaufort Sea. After year 3, only ice road #1 would be constructed to allow additional materials and equipment to be
mobilized to support LDPI, pipeline, and facility construction activities as all island construction and pipeline installation should be complete by year 3. Winter sea ice road/trail construction will begin as early as possible (typically December 1 through mid-February). It is anticipated that all ice road construction activities will be initiated prior to March 1, before the time when female ringed seals establish birth lairs.
In addition to the ice roads, three ice pads are proposed to support construction activities (year 2 and 3). These would be used to support LDPI, pipeline, (including pipe stringing and two stockpile/disposal areas) and facilities construction. A fourth staging area ice pad (approximately 350 feet by 700 feet) would be built on the sea ice on the west side of the LDPI during production well drilling operations.
Other on-ice activities occurring prior to March 1 could also include spill training exercises, pipeline surveys, snow clearing, and work conducted by other snow vehicles such as a Pisten Bully, snow machine, or rollagon. Prior to March 1, these activities could occur outside of the delineated ice road/trail and shoulder areas.
LDPI Construction
The LDPI will include a self-contained offshore drilling and production facility located on an artificial gravel island with a subsea pipeline to shore. The LDPI will be located approximately 8 kilometers (km) or 5 miles (mi) offshore in Foggy Island Bay and 11.7 km (7.3 mi) southeast of the existing SDI on the Endicott causeway (see Figure 1). The LDPI will be constructed of reinforced gravel in 5.8 meters (m) (19 feet (ft)) of water and have a working surface of approximately 3.8 hectares (ha) (9.3 acres (ac)). A steel sheet pile wall would surround the island to stabilize the placed gravel and the island would include slope protection bench, dock and ice road access and a seawater intake area (Figure 2).
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Hilcorp would begin constructing the LDPI during the winter immediately following construction of the ice road from the mine site to the island location. Sections of sea ice at the island's location would be cut using a ditchwitch and removed. A backhoe and support trucks using the ice road would move ice away. Once the ice is removed, gravel will be poured through the water column to the sea floor, building the island structure from the bottom up. A conical pile of gravel (hauled in from trucks from the mine site using the ice road) will form on the sea floor until it reaches the surface of the ice. Gravel hauling over the ice road to the LDPI construction site is estimated to continue for 50 to 70 days, and conclude mid-April or earlier depending on road conditions. The construction would continue with a sequence of removing additional ice and pouring gravel until the surface size is achieved. Following gravel placement, slope armoring and protection installation would occur. Using island-based equipment (
e.g.,
backhoe, bucket-dredge) and divers, Hilcorp would create a slope protection profile consisting of a 60-ft (18.3 m) wide bench covered with a linked concrete mat that
extends from a sheet pile wall surrounding the island to slightly above mean low low water (MLLW) (Figure 3). The linked concrete mat requires a high strength, yet highly permeable woven polyester fabric under layer to contain the gravel island fill. The filter fabric panels will be overlapped and tied together side-by-side (requiring diving operations) to prevent the panels from separating and exposing the underlying gravel fill. Because fabric is overlapped and tied together, no slope protection debris would enter the water column should it be damaged. Above the fabric under layer, a robust geo-grid will be placed as an abrasion guard to prevent damage to the fabric by the linked mat armor. The concrete mat system would continue another at a 3:1 slope another 86.5 ft into the water, terminating at a depth of −19 ft (−5.8 m). In total, from the sheet pile wall, the bench and concrete mat would extend 146.5 ft. Island slope protection is required to assure the integrity of the gravel island by protecting it from the erosive forces of waves, ice ride-up, and currents. A detailed inspection of the island slope protection system will be conducted annually during the open-water season to document changes in the condition of the island slope protection system that have occurred since the previous year's inspection. Any damaged material would be removed. Above-water activities will consist of a visual inspection of the dock and sheet pile enclosure, and documenting the condition of the island bench and ramps. The below-water slopes will be inspected by divers or if water clarity allows, remotely by underwater cameras contracted separately by Hilcorp. The results of the below water inspection will be recorded for repair if needed. No vessels will be required. Multi-beam bathymetry and side-scan sonar imagery of the below-water slopes and adjacent sea bottom will be acquired using a bathymetry vessel. The sidescan sonar would operate at a frequency between 200-400 kilohertz (kHz). The single-beam echosounder would operate at a frequency of about 210 kHz.
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Once the slope protection is in place, Hilcorp would install the sheet pile wall around the perimeter of the island using vibratory and, if necessary, impact hammers. Hilcorp anticipates driving up to 20 piles per day to a depth of 25 ft. A vibratory hammer would be used first followed by an impact hammer to “proof” the pile. Hilcorp anticipates each pile needing 100 hammer strikes over approximately 2 minutes of impact driving to obtain final desired depth for each sheet pile. Per day, this equates to a maximum of 40 minutes and 2,000 strikes of impact hammering per day. For vibratory driving, pile penetration speed can vary depending on ground conditions, but a minimum sheet pile penetration speed is 20 inches (0.5 m) per minute to avoid damage to pile or hammer (NASSPA 2005). For this project, the anticipated duration is based on a preferred penetration speed greater than 40 inches (1 m) per minute, resulting in 7.5 minutes to drive each pile. Given the high storm surge and larger waves that are expected to arrive at the LDPI site from the west and northwest, the wall will be higher on the west side than on the east side. At the top of the sheet-pile wall, overhanging steel “parapet” will be installed to prevent wave passage over the wall.
Within the interior of the island, 16 steel conductor pipes would be driven to a depth of 160 ft (49 m) to provide the initial stable structural foundation for each oil well. They would be set in a well row in the middle of the island. Depending on the substrate the conductor pipes would be driven by impact or vibratory methods or both. During construction of the nearby Northstar Island (located in deeper water), it took 5 to 8.5 hours to drive one conductor pipe (Blackwell
et al.,
2004). For the Liberty LDPI, Hilcorp anticipates it would take two hours of active pile driving per day to install a conductor pipe given the 5 to 8.5 hour timeframe at Northstar includes pauses in pile driving and occurred in deeper water requiring deeper pile depths. In addition, approximately 700 to 1,000 foundation piles may also be installed within the interior of the island should engineering determine they are necessary for island support.
Pipeline Installation
Hilcorp would install a pipe-in-pipe subsea pipeline consisting of a 12-in diameter inner pipe and a 16-in diameter outer pipe to transport oil from the LDPI to the existing Bandami pipeline. Pipeline construction is planned for the winter after the island is constructed. A schematic of the pipeline can be found in Figure 2-3 of BOEM's Final EIS available at
https://www.boem.gov/Hilcorp-Liberty
/. The pipeline will extend from the LDPI, across Foggy Island Bay, and terminate onshore at the existing Badami Pipeline tie-in location. For the marine segment, construction will progress from shallower water to deeper water with multiple construction spreads.
To install the pipeline, a trench will be excavated using ice-road based long reach excavators with pontoon tracks. The pipeline bundle will be lowered into the trench using side booms to control its vertical and horizontal position, and the trench will be backfilled by excavators using excavated trench spoils and select backfill. Hilcorp intends to place all material back in the trench slot. All work will be done from ice roads using conventional excavation and dirt-moving construction equipment. The target trench depth is 9 to 11 ft (2.7 to 3.4 m) with a proposed maximum depth of cover of approximately 7 ft (2.1 m). The pipeline will be approximately 5.6 mi (9 km) long. Hydro-testing (pressure testing using sea water) of the entire pipeline will be completed prior to commissioning.
Drilling and Production
The final drill rig has yet to be chosen by Hilcorp but has been narrowed to two options and will accommodate drilling of 16 wells. The first option is the use of an existing platform-style drilling unit that Hilcorp owns and operates in the Cook Inlet. Designated as Rig 428, the rig has been used recently and is well suited in terms of depth and horsepower rating to drill the wells at Liberty. A second option that is being investigated is a new build drilling unit that would be built to not only drill Liberty development wells, but would be more portable and more adaptable to other applications on the North Slope. Regardless of drill rig type, the well row arrangement on the island is designed to accommodate up to 16 wells. We note that while Hilcorp is proposing a 16 well design, only 10 wells would be drilled. The 6 additional well slots would be available as backups or for potential in-fill drilling if needed during the project life.
Process facilities on the island will separate crude oil from produced water and gas. Gas and water will be injected into the reservoir to provide pressure support and increase recovery from the field. A single-phase subsea pipe-in-pipe pipeline will transport sales-quality crude from the LDPI to shore, where an aboveground pipeline will transport crude to the existing Badami pipeline. From there, crude will be transported to the Endicott Sales Oil Pipeline, which ties into Pump Station 1 of the TransAlaska Pipeline System (TAPS) for eventual delivery to a refinery.
Description of Marine Mammals in the Area of the Specified Activity
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' Stock Assessment Reports (SARs;
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments
) and more general information about these species (
e.g.,
physical and behavioral descriptions) may be found on NMFS' website (
www.nmfs.noaa.gov/pr/species/mammals/
). Additional information may be found in BOEM's Final EIS for the project which is available online at
https://www.boem.gov/Hilcorp-Liberty/.
Table 2 lists all species with expected potential for occurrence in Foggy Island Bay and surrounding Beaufort Sea 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). 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' U.S. 2017 SAR for Alaska (Muto
et al.,
2018). All values presented in Table 2 are the most recent available at the time of publication and are available in the 2017 SARs (Muto
et al.,
2018).
Table 2—Marine Mammals With Expected Potential Occurrence in Beaufort Sea, Alaska
Common name
Scientific name
Stock
ESA/MMPA
status;
strategic
(Y/N)
1
Stock abundance )
(CV, N
min
, most recent abundance survey)
2
PBR
Annual
M/SI
3
Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales)
Family Eschrichtiidae
Gray whale
Eschrichtius robustus
Eastern North Pacific
-;N
20,990 (0.05, 20,125, 2011)
624
132
Family Balaenidae
Bowhead whale
Balaena mysticetus
Western Arctic
E/D; Y
16,820 (0.052, 16,100, 2011)
161
46
Humpback whale
Megaptera novaeangliae
Central North Pacific Stock
E/D; Y
10,103 (0.3, 7,891, 2006)
83
26
Minke whale
Alaska
-;N
unk
undet
0
Fin whale
Northeast Pacific
E/D; Y
3,168 (0.26, 2,554, 2013)
6
5.1
0.6
Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
Family Delphinidae
Beluga whale
Delphinapterus leucas
Beaufort Sea
-; N
39,258 (0.229, N/A, 1992)
Und
139
Eastern Chukchi
-; N
20,752 (0.70, 12,194, 2012)
244
67
Killer whale
Orcinus orcas
Eastern North Pacific Gulf of Alaska, Aleutian Islands, and Bering Sea Transient
-;N
587 (n/a, 587, 2012)
5.9
0
Order Carnivora—Superfamily Pinnipedia
Family Otariidae (eared seals and sea lions)
Steller sea lion
Eumatopias jubatus
Eastern U.S
-; N
41,638 (-, 41,638, 2015)
2,498
108
Western U.S
E/D;Y
53,303 (-, 53,303, 2016)
320
241
Family Phocidae (earless seals)
Ringed Seal
Pusa hispida
Alaska
T, D; Y
170,000 (-, 170,000, 2012)
4
Und
1,054
Bearded seal
Erignathus barbatus
Alaska
T, D; Y
299,174 (-, 273,676)
5
Und
391
Spotted seal
Phoca largha
Alaska
423,625 (-, 423,237, 2013)
12,697
329
Ribbon seal
Histriophoca fasciata
Alaska
184,000 (-, 163,086, 2013)
9,785
3.9
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.
3
These values, found in NMFS' SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (
e.g.,
subsistence use, 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.
4
The population provided here was derived using a using a very limited sub-sample of the data collected from the U.S. portion of the Bering Sea in 2012 (Conn
et al.,
2014). Thus, the actual number of ringed seals in the U.S. sector of the Bering Sea is likely much higher, perhaps by a factor of two or more (Muto
et al.,
2018). Reliable estimates of abundance are not available for the Chukchi and Beaufort seas (Muto
et al.,
2018).
5
5. In spring of 2012 and 2013, surveys were conducted in the Bering Sea and Sea of Okhotsk; these data do not include seals in the Chukchi and Beaufort Seas at the time of the survey.
6
N
BEST
, N
MIN
, and PBR have been calculated for this stock; however, important caveats exist. See Stock Assessment Report text for details.
Note—
Italicized species are not expected to be taken or proposed for authorization.
All species that could potentially occur in the Beaufort Sea are included in Table 2. However, the temporal and/or spatial occurrence of minke, fin, humpback whales, killer whales, narwhals, harbor porpoises, and ribbon seals are such that take is not expected to occur, and they are not discussed further beyond the explanation provided here. These species, regularly occur in the Chukchi Sea but not as commonly in the Beaufort Sea. Narwhals, Steller sea lions, and hooded seals are considered extralimital to the proposed action area These species could occur in the Beaufort Sea, but are either uncommon or extralimital east of Barrow (located in the Foggy Island Bay area and surveys within the Bay have revealed zero sightings).
In addition, the polar bear may be found in Foggy Island Bay. However, this species is managed by the U.S. Fish and Wildlife Service and is not considered further in this document.
On October 11, 2016, NOAA released the Final Environmental Impact Statement (FEIS) for the Effects of Oil and Gas Activities in the Arctic Ocean (81 FR 72780, October 21, 2016) regarding geological and geophysical (
i.e.,
seismic) activities, ancillary activities, and exploratory drilling. The Final EIS may be found at
https://www.fisheries.noaa.gov/national/marine-mammal-protection/environmental-impact-statement-eis-effects-oil-and-gas-activities.
Although no seismic activities are proposed by Hilcorp, the EIS contains detailed
information on marine mammal species proposed to be potentially taken by Hilcorp's specified activities. More recently, BOEM released a final EIS on the Liberty Project. We incorporate by reference the information on the species proposed to be potentially taken by Hilcorp's specified activities from these documents and provide a summary and any relevant updates on species status here.
Bowhead Whale
The only bowhead whale stock found within U.S. waters is the Western Arctic stock, also known as the Bering-Chukchi-Beaufort stock (Rugh
et al.,
2003) or Bering Sea stock (Burns
et al.,
1993). The majority of the Western Arctic stock migrates annually from wintering areas (December to March) in the northern Bering Sea, through the Chukchi Sea in the spring (April through May), to the eastern Beaufort Sea where they spend much of the summer (June through early to mid-October) before returning again to the Bering Sea in the fall (September through December) to overwinter (Braham
et al.,
1980, Moore and Reeves 1993, Quakenbush
et al.,
2010a, Citta
et al.,
2015). Some bowhead whales are found in the western Beaufort, Chukchi, and Bering seas in summer, and these are thought to be a part of the expanding Western Arctic stock (Rugh
et al.,
2003; Clarke
et al.,
2013, 2014, 2015; Citta
et al.,
2015). The most recent population parameters (
e.g.,
abundance, PBR) of western Arctic bowhead whales are provided in Table 2.
Bowhead whale distribution in the Beaufort Sea during summer-fall has been studied by aerial surveys through the Bowhead Whale Aerial Survey Project (BWASP). This project was funded or contracted by the Minerals Management Service (MMS)/Bureau of Ocean Energy Management (BOEM) and Bureau of Land Management (BLM) annually from 1979 to 2010. The focus of the BWASP aerial surveys was the autumn migration of bowhead whales through the Alaskan Beaufort Sea, although data were collected on all marine mammals sighted. The NMFS National Marine Mammal Laboratory (NMML) began coordinating BWASP in 2007, with funding from MMS. In 2011, an Interagency Agreement between the BOEM and NMML combined BWASP with COMIDA under the auspices of a single survey called Aerial Surveys of Arctic Marine Mammals (ASAMM) (Clarke
et al.,
2012); both studies are funded by BOEM. In September to mid-October bowheads begin their western migration out of the Canadian Beaufort Sea to the Chukchi Sea (Figure 3.2-10). Most westward travel across the Beaufort Sea by tagged whales was over the shelf, within 100 km (62 mi) of shore, although a few whales traveled farther offshore (Quakenbush
et al.,
2012).
During winter and spring, bowhead whales are closely associated with sea ice (Moore and Reeves 1993, Quakenbush
et al.,
2010a, Citta
et al.,
2015). The bowhead whale spring migration follows fractures in the sea ice around the coast of Alaska, generally in the shear zone between the shorefast ice and the mobile pack ice. During summer, most of the population is in relatively ice-free waters in the southeastern Beaufort Sea (Citta
et al.,
2015), an area often exposed to industrial activity related to petroleum exploration (
e.g.,
Richardson
et al.,
1987, Davies, 1997). Summer aerial surveys conducted in the western Beaufort Sea during July and August of 2012-2014 have had relatively high sighting rates of bowhead whales, including cows with calves and feeding animals (Clarke
et al.,
2013, 2014, 2015). During the autumn migration through the Beaufort Sea, bowhead whales generally select shelf waters (Citta
et al.,
2015). In winter in the Bering Sea, bowhead whales often use areas with ~100 percent sea-ice cover, even when polynyas are available (Quakenbush
et al.,
2010a, Citta
et al.,
2015).
From 2006 through 2014, median distance of bowhead whales from shore was 23.6 km (14.7 mi) in the East Region and 24.2 km (15.0 mi) in the West Region during previous low-ice years, with annual median distances ranging from as close as 6.3 km (3.9 mi) in 2009 to 37.6 km (23.4 mi) in 2013 (Clarke
et al.,
2015b). Median depth of sightings during previous low-ice years was 39 m (128 ft) in the East Region and 21 m (69 ft) in the West Region; in 2014, median depth of on-transect sightings was 20 m (66 ft) and 19 m (62 ft), respectively (Clarke
et al.,
2015b). In September and October 2014, bowhead whales in the East Region of the study area were sighted in shallower water and closer to shore than in previous years of light sea ice cover; in the West Region, bowhead sightings in fall 2014 were in shallower water than in previous light ice years, but the distance from shore did not differ (Clarke
et al.,
2015b). Behaviors included milling, swimming, and feeding, to a lesser degree. Highest numbers of sightings were in the central Beaufort Sea and east of Point Barrow. Overall, the most shoreward edge of the bowhead migratory corridor for bowhead extends approximately 40 km (25 mi) north from the barrier islands, which are located approximately 7 km (4 mi) north of Liberty Project. The closest approach of a tagged whale occurred in August 2016 when it came within 16 km of the proposed LDPI (Quakenbush, 2018).
Historically, there have been few spring, summer, or autumn observations of bowheads in larger bays such as Camden, Prudhoe, and Harrison Bays, although some groups or individuals have occasionally been observed feeding around the periphery of or, less commonly, inside the bays as migration demands and feeding opportunities permit. Observations indicate that juvenile, sub-adult, and cow-calf pairs of bowheads are the individuals most frequently observed in bays and nearshore areas of the Beaufort, while more competitive whales are found in the Canadian Beaufort and Barrow Canyon, as well as deeper offshore waters (Clarke
et al.,
2011b, 2011c, 2011d, 2012, 2013, 2014, 2015b; Koski and Miller, 2009; Quakenbush
et al.,
2010).
Clarke
et al.
(2015) evaluated biologically important areas (BIAs) for bowheads in the U.S. Arctic region and identified nine BIAs. The spring (April-May) migratory corridor BIA for bowheads is far offshore of the LDPI but within the transit portion of the action area, while the fall (September-October) migratory corridor BIA (western Beaufort on and north of the shelf) for bowheads is further inshore and closer to the LDPI. Clarke
et al.
(2015) also identified four BIAs for bowheads that are important for reproduction and encompassed areas where the majority of bowhead whales identified as calves were observed each season; none of these reproductive BIAs overlap with the LDPI, but may be encompassed in indirect areas such as vessel transit route. Finally, three bowhead feeding BIAs were identified. Again, there is no spatial overlap of the activity area with these BIAs.
From July 8, 2008, through August 25, 2008, BPXA conducted a 3D seismic survey in the Liberty Prospect, Beaufort Sea. During the August survey a mixed-species group of whales was observed in one sighting near the barrier islands that included bowhead and gray whales (Aerts
et al.,
2008). This is the only known survey sighting of bowhead whales within Foggy Island Bay despite industry surveys occurring during the open water season in 2010, 2014, and 2015 and NMFS aerial surveys flown inside Foggy Island Bay in 2016 and 2017.
Alaska Natives have been taking bowhead whales for subsistence purposes for at least 2,000 years (Marquette and Bockstoce, 1980, Stoker
and Krupnik, 1993). Subsistence takes have been regulated by a quota system under the authority of the IWC since 1977. Alaska Native subsistence hunters, primarily from 11 Alaska communities, take approximately 0.1-0.5 percent of the population per annum (Philo
et al.,
1993, Suydam
et al.,
2011). The average annual subsistence take (by Natives of Alaska, Russia, and Canada) during the 5-year period from 2011 through 2015 is 43 landed bowhead whales (Muto
et al.,
2018).
Gray Whale
The eastern North Pacific population of gray whales migrates along the coasts of eastern Siberia, North America, and Mexico (Allen and Angliss 2010; Weller
et al.,
2002) and population size has been steadily increasing, potentially reaching carrying capacity (Allen and Angliss, 2010, 2012). Abundance estimates will likely rise and fall in the future as the population finds a balance with the carrying-capacity of the environment (Rugh
et al.,
2005). The steadily increasing population abundance warranted delisting of the eastern North Pacific gray whale stock in 1994, as it was no longer considered endangered or threatened under the ESA (Rugh
et al.,
1999). A five-year status review determined that the stock was neither in danger of extinction nor likely to become endangered in the foreseeable future, thus, retaining the non-threatened classification (Rugh
et al.,
1999). Table 2 provided population parameters for this stock.
The gray whale migration may be the longest of any mammalian species. They migrate over 8,000 to 10,000 km (5,000 to 6,200 mi) between breeding lagoons in Mexico and Arctic feeding areas each spring and fall (Rugh
et al.,
1999). The southward migration out of the Chukchi Sea generally begins during October and November, passing through Unimak Pass in November and December, then continues along a coastal route to Baja California (Rice
et al.,
1984). The northward migration usually begins in mid-February and continues through May (Rice
et al.
1984).
Gray whales are the most coastal of all the large whales and inhabit primarily inshore or shallow, offshore continental shelf waters (Jones and Swartz, 2009); however, they are more common in the Chukchi than in the Beaufort Sea. Throughout the summers of 2010 and 2011, gray whales regularly occurred in small groups north of Point Barrow and west of Barrow (George
et al.,
2011; Shelden
et al.,
2012). In 2011, there were no sightings of gray whales east of Point Barrow during ASAMM aerial surveys (Clarke
et al.,
2012); however, they were observed east of Point Barrow, primarily in the vicinity of Barrow Canyon, from August to October 2012 (Clarke
et al.,
2013). Gray whales were again observed east of Point Barrow in 2013, with all sightings in August except for one sighting in late October (Clarke
et al.,
2014). In 2014, sightings in the Beaufort Sea included a few whales east of Point Barrow and one north of Cross Island near Prudhoe Bay (Clarke
et al.,
2015b). Gray whales prefer shoal areas (<60 m (197 ft) deep) with low (<7 percent) ice cover (Moore and DeMaster, 1997). These areas provide habitat rich in gray whale prey (amphipods, decapods, and other invertebrates).
From July 8, 2008 through August 25, 2008, BPXA conducted a 3D seismic survey in the Liberty Prospect, Beaufort Sea. During the August survey a mixed-species group of whales was observed in one sighting near the barrier islands that included bowhead and gray whales (Aerts
et al.,
2008). This is the only known survey sighting of gray whales within Foggy Island Bay despite industry surveys occurring during the open water season in 2010, 2014, and 2015 and NMFS aerial surveys flown inside Foggy Island Bay in 2016 and 2017.
Beluga Whale
Five beluga whale stocks are present in Alaska including the Cook Inlet, Bristol Bay, eastern Bering Sea, eastern Chukchi Sea, and Beaufort Sea stocks (O'Corry-Crowe
et al.,
1997, Allen and Angliss, 2015). The eastern Chukchi and Beaufort Sea stocks are thought to overlap in the Beaufort Sea. Both stocks are closely associated with open leads and polynyas in ice-covered regions throughout Arctic and sub-Arctic waters of the Northern Hemisphere. Distribution varies seasonally. Whales from both the Beaufort Sea and eastern Chukchi Sea stocks overwinter in the Bering Sea. Belugas of the eastern Chukchi may winter in offshore, although relatively shallow, waters of the western Bering Sea (Richard
et al.,
2001), and the Beaufort Sea stock may winter in more nearshore waters of the northern Bering Sea (R. Suydam, pers. comm. 2012c). In the spring, belugas migrate to coastal estuaries, bays, and rivers. Annual migrations may cover thousands of kilometers (Allen and Angliss, 2010, 2012a).
Satellite telemetry data from 23 whales tagged in Kaseguluk Lagoon in 1998 through 2002 provided information on movements and migrations of eastern Chukchi Sea belugas. Animals initially traveled north and east into the northern Chukchi and western Beaufort seas after capture (Suydam
et al.,
2001, 2005). Movement patterns between July and September vary by age and/or sex classes. Adult males frequent deeper waters of the Beaufort Sea and Arctic Ocean (79-80° N), where they remain throughout the summer. Immature males moved farther north than immature females but not as far north as adult males. All of the belugas frequented water deeper than 200 m (656 ft) along and beyond the continental shelf break. Use of the inshore waters within the Beaufort Sea Outer Continental Shelf lease sale area was rare (Suydam
et al.,
2005).
Most information on distribution and movements of belugas of the Beaufort Sea stock was similarly derived using satellite tags. A total of 30 belugas were tagged in the Mackenzie River Delta, Northwest Territories, Canada, during summer and autumn in 1993, 1995, and 1997 (Richard
et al.,
2001). Approximately half of the tagged whales traveled far offshore of the Alaskan coastal shelf, while the remainder traveled on the shelf or near the continental slope (Richard
et al.,
2001). Migration through Alaskan waters lasted an average of 15 days. In 1997, all of the tagged belugas reached the western Chukchi Sea (westward of 170° W) between September 15 and October 9. Overall, the main fall migration corridor for beluga whales is believed to be approximately 62 mi (100 km) north of the Project Area (Richard
et al.,
1997, 2001). Both the spring (April-May) and fall (September-October) migratory corridor BIAs for belugas are far north of the proposed action area because sightings of belugas from aerial surveys in the western Beaufort Sea are primarily on the continental slope, with relatively few sightings on the shelf (Clarke
et al.,
2015). No reproductive and feeding BIAs exist for belugas in the action area (Clarke
et al.,
2015).
O'Corry
et al.
(2018) studied genetic marker sets in 1,647 beluga whales. The data set was from over 20 years and encompassed all of the whales' major coastal summering regions in the Pacific Ocean. The genetic marker analysis of the migrating whales revealed that while both the wintering and summering areas of the eastern Chukchi Sea and eastern Beaufort Sea subpopulations may overlap, the timing of spring migration differs such that the whales hunted at coastal sites in Chukotka, the Bering Strait (
i.e.,
Diomede), and northwest Alaska (
i.e.,
Point Hope) in the spring and off of Alaska's Beaufort Sea coast in summer were predominantly from the eastern Beaufort Sea population. Earlier genetic investigations and recent telemetry
studies show that the spring migration of eastern Beaufort whales occurs earlier and through denser sea ice than eastern Chukchi Sea belugas. The discovery that a few individual whales found at some of these spring locations had higher likelihood of having eastern Chukchi Sea ancestry or being of mixed-ancestry, indicates that the Bering Strait region is also an area where the stock mix in spring. Citta
et al.
(2016) also observed that tagged eastern Beaufort Sea whales migrated north in spring through the Bering Strait earlier than the eastern Chukchi belugas so they had to pass through the latter's primary wintering area. Therefore, the eastern Chukchi stock should not be present in the action area at any time in general, but especially during summer-late fall, when the beluga exposures would be anticipated for this project. Therefore, we assume all belugas impacted by the proposed project are from the Beaufort Sea stock.
Beluga whales were regularly sighted during the September-October BWASP and the more recent ASAMM aerial surveys of the Alaska Beaufort Sea coast. Burns and Seaman (1985) suggest that beluga whales are strongly associated with the ice fringe and that the route of the autumn migration may be mainly determined by location of the drift ice margin. Relatively few beluga whales have been observed in the nearshore areas (on the continental shelf outside of the barrier islands) of Prudhoe Bay. However, groups of belugas have been detected nearshore in September (Clarke
et al.,
2011a) and opportunistic sightings have been recorded from Northstar Island and Endicott. These sightings are part of the fall migration which generally occurs farther offshore although a few sightings of a few individuals do occur closer to the shore, and occasionally inside the barrier islands of Foggy Island Bay. During the 2008 seismic survey in Foggy Island Bay, three sightings of eight individuals were observed at a location about 3 mi (4.8 km) east of the Endicott Satellite Drilling Island (Aerts
et al.,
2008). In 2014, during a BPXA 2D HR shallow geohazard survey in July and August, PSOs recorded eight groups of approximately 19 individual beluga whales, five of which were juveniles (Smultea
et al.,
2014). During the open water season July 9 through July 19, 2015, five sightings of belugas occurred (Cate
et al.,
2015). Also in 2015, acoustic monitoring was conducted in Foggy Island Bay between July 6 and September 22, 2015, to characterize ambient sound conditions and to determine the acoustic occurrence of marine mammals near Hilcorp's Liberty Prospect in Foggy Island Bay (Frouin-Jouy
et al.,
2015). Two recorders collected underwater sound data before, during, and after Hilcorp's 2015 geohazard survey (July 6-Sept. 22). Detected marine mammal vocalizations included those from beluga whales and pinnipeds. Belugas were detected on five days by passive-recorders inside the bay during the three-month survey period (Frouin-Jouy
et al.,
2015). During the 2016 and 2017 ASAMM surveys flown inside Foggy Island Bay, no belugas were observed. Beluga whales are the cetacean most likely to be encountered during the open-water season in Foggy Island Bay, albeit few in abundance.
Ringed Seal
One of five Arctic ringed seal stocks, the Alaska stock, occurs in U.S. waters. The Arctic subspecies of ringed seals was listed as threatened under the ESA on December 28, 2012, primarily due to expected impacts on the population from declines in sea and snow cover stemming from climate change within the foreseeable future (77 FR 76706). However, on March 11, 2016, the U.S. District Court for the District of Alaska issued a decision in a lawsuit challenging the listing of ringed seals under the ESA (
Alaska Oil and Gas Association et al.
v.
National Marine Fisheries Service,
Case No. 4:14-cv-00029-RRB). The decision vacated NMFS' listing of Arctic ringed seals as a threatened species. However, on February 12, 2018, in
Alaska Oil & Gas Association
v.
Ross
, Case No. 16-35380, the U.S. Court of Appeals for the Ninth Circuit reversed the district court's 2016 decision. As such, Arctic ringed seals remain listed as threatened under the ESA.
During winter and spring in the United States, ringed seals are found throughout the Beaufort and Chukchi Seas; they occur in the Bering Sea as far south as Bristol Bay in years of extensive ice coverage. Most ringed seals that winter in the Bering and Chukchi Seas are thought to migrate northward in spring with the receding ice edge and spend summer in the pack ice of the northern Chukchi and Beaufort Seas.
Ringed seals are resident in the Beaufort Sea year-round, and based on results of previous surveys in Foggy Island Bay (Aerts
et al.,
2008, Funk
et al.,
2008, Savarese
et al.,
2010, Smultea
et al.,
2014), and monitoring from Northstar Island (Aerts and Richardson, 2009, 2010), they are expected to be the most commonly occurring pinniped in the action area year-round.
Ringed seals are present in the nearshore and sea ice year-round, maintaining breathing holes and excavating subnivean lairs in the landfast ice during the ice-covered season. Ringed seals overwinter in the landfast ice in and around the LDPI action area. There is some evidence indicating that ringed seal densities are low in water depths of less than 3 m, where landfast ice extending from the shoreline generally freezes to the sea bottom in very shallow waters during the course of the winter (Moulton
et al.,
2002a, Moulton
et al.,
2002b, Richardson and Williams, 2003). Ringed seals that breed on shorefast ice may either forage within 100 km (62.1 mi) of their breeding habitat or undertake extensive foraging trips to more productive areas at distances of between 100-1,000 kilometers (Kelly
et al.,
2010b). Adult Arctic ringed seals show site fidelity, returning to the same subnivean site after the foraging period ends. Movements are limited during the ice-bound months, including the breeding season, which limits their foraging activities and may minimize gene flow within the species (Kelly
et al.
2010b). During April to early June (the reproductive period), radio-tagged ringed seals inhabiting shorefast ice near Prudhoe Bay had home range sizes generally less than 1,336 ac (500 ha) in area (Kelly
et al.,
2005). Sub-adults, however, were not constrained by the need to defend territories or maintain birthing lairs and followed the advancing ice southward to winter along the Bering Sea ice edge where there may be enhanced feeding opportunities and less exposure to predation (Crawford
et al.,
2012). Sub-adult ringed seals tagged in the Canadian Beaufort Sea similarly undertook lengthy migrations across the continental shelf of the Alaskan Beaufort Sea into the Chukchi Sea, passing Point Barrow prior to freeze-up in the central Chukchi Sea (Harwood
et al.,
2012). Factors most influencing seal densities during May through June in the central Beaufort Sea between Oliktok Point and Kaktovik were water depth, distance to the fast ice edge, and ice deformation. Highest densities of seals were at depths of 5 to 35 m (16 to 144 ft) and on relatively flat ice near the fast ice edge (Frost
et al.,
2004).
Sexual maturity in ringed seals varies with population status. It can be as early as 3 years for both sexes and as late as 7 years for males and 9 years for females. Ringed seals breed annually, with timing varying regionally. Mating takes place while mature females are still nursing their pups on the ice and
is thought to occur under the ice near birth lairs. In all subspecies except the Okhotsk, females give birth to a single pup hidden from view within a snow-covered birth lair. Ringed seals are unique in their use of these birth lairs. Pups learn how to dive shortly after birth. Pups nurse for 5 to 9 weeks and, when weaned, are four times their birth weights. Ringed seal pups are more aquatic than other ice seal pups and spend roughly half their time in the water during the nursing period (Lydersen and Hammill, 1993). Pups are normally weaned before the break-up of spring ice.
Ringed seals are an important resource for Alaska Native subsistence hunters. Approximately 64 Alaska Native communities in western and northern Alaska, from Bristol Bay to the Beaufort Sea, regularly harvest ice seals (Ice Seal Committee, 2016). Based on the harvest data from 12 Alaska Native communities, a minimum estimate of the average annual harvest of ringed seals in 2009-2013 is 1,050 seals (Muto
et al.,
2016).
Other sources of mortality include commercial fisheries and predation by marine and terrestrial predators including polar bears, arctic foxes, walrus, and killer whales. During 2010-2014, incidental mortality and serious injury of ringed seals was reported in 4 of the 22 federally-regulated commercial fisheries in Alaska monitored for incidental mortality and serious injury by fisheries observers: the Bering Sea/Aleutian Islands flatfish trawl, Bering Sea/Aleutian Islands pollock trawl, Bering Sea/Aleutian Islands Pacific cod trawl, and Bering Sea/Aleutian Islands Pacific cod longline fisheries (Muto
et al.,
2016). From May 1, 2011 to December 31, 2016, 657 seals, which included 233 dead stranded seals, 179 subsistence hunted seals, and 245 live seals, stranded or were sampled during permitted health assessments studies. Species involved were primarily ice seals including ringed, bearded, ribbon, and spotted seals in northern and western Alaska. The investigation identified that clinical signs were likely due to an abnormality of the molt, but a definitive cause for the abnormal molt was not determined.
Bearded Seal
Two subspecies of bearded seal have been described:
E. b. barbatus
from the Laptev Sea, Barents Sea, North Atlantic Ocean, and Hudson Bay (Rice 1998); and
E. b. nauticus
from the remaining portions of the Arctic Ocean and the Bering and Okhotsk seas (Ognev, 1935, Scheffer, 1958, Manning, 1974, Heptner
et al.,
1976). On December 28, 2012, NMFS listed two distinct population segments (DPSs) of the
E. b. nauticus
subspecies of bearded seals—the Beringia DPS and Okhotsk DPS—as threatened under the ESA (77 FR 76740). Similar to ringed seals, the primary concern for these DPSs is the ongoing and projected loss of sea-ice cover stemming from climate change, which is expected to pose a significant threat to the persistence of these seals in the foreseeable future (based on projections through the end of the 21st century; Cameron
et al.,
2010). Similar to ringed seals, the ESA listing of the Beringia and Okhotsk DPSs of bearded seal was challenged in the U.S. District Court for the District of Alaska, and on July 25, 2014, the court vacated NMFS' listing of those DPSs of bearded seals as threatened under the ESA (
Alaska Oil and Gas Association et al.
v.
Pritzker,
Case No. 4:13-cv-00018-RRB). However, the U.S. Court of Appeals for the Ninth Circuit reversed the district court's 2016 decision on October 24, 2016 (
Alaska Oil & Gas Association
v.
Pritzer
, Case No. 14-35806). As such, the Beringia and Okhotsk DPSs of bearded seal remain listed as threatened under the ESA.
For the purposes of MMPA stock assessments, the Beringia DPS is considered the Alaska stock of the bearded seal (Muto
et al.,
2016). The Beringia DPS of the bearded seal includes all bearded seals from breeding populations in the Arctic Ocean and adjacent seas in the Pacific Ocean between 145° E longitude (Novosibirskiye) in the East Siberian Sea and 130° W longitude in the Canadian Beaufort Sea, except west of 157° W longitude in the Bering Sea and west of the Kamchatka Peninsula (where the Okhotsk DPS is found). They generally prefer moving ice that produces natural openings and areas of open-water (Heptner
et al.,
1976, Fedoseev, 1984, Nelson
et al.,
1984). They usually avoid areas of continuous, thick, shorefast ice and are rarely seen in the vicinity of unbroken, heavy, drifting ice or large areas of multi-year ice (Fedoseev, 1965, Burns and Harbo, 1972, Burns and Frost, 1979, Burns, 1981, Smith, 1981, Fedoseev, 1984, Nelson
et al.,
1984).
Spring surveys conducted in 1999-2000 along the Alaska coast indicate that bearded seals are typically more abundant 20-100 nautical miles (nmi) from shore than within 20 nmi from shore, except for high concentrations nearshore to the south of Kivalina (Bengtson
et al.,
2005; Simpkins
et al.,
2003).
Although bearded seal vocalizations (produced by adult males) have been recorded nearly year-round in the Beaufort Sea (MacIntyre
et al.,
2013, MacIntyre
et al.,
2015), most bearded seals overwinter in the Bering Sea. In addition, during late winter and early spring, Foggy Island Bay is covered with shorefast ice and the nearest lead systems are at least several kilometers away, making the area unsuitable habitat for bearded seals. Therefore, bearded seals are not expected to be encountered in or near the LDPI portion of the action area during this time (from late winter through early spring).
During the open-water period, the Beaufort Sea likely supports fewer bearded seals than the Chukchi Sea because of the more extensive foraging habitat available to bearded seals in the Chukchi Sea. In addition, as a result of shallow waters, the sea floor in Foggy Island Bay south of the barrier islands is often scoured by ice, which limits the presence of bearded seal prey species. Nevertheless, aerial and vessel-based surveys associated with seismic programs, barging, and government surveys in this area between 2005 and 2010 reported several bearded seal sightings (Green and Negri, 2005, Green and Negri 2006, Green
et al.,
2007, Funk
et al.,
2008, Hauser
et al.,
2008, Savarese
et al.,
2010, Clarke
et al.,
2011, Reiser
et al.,
2011). In addition, eight bearded seal sightings were documented during shallow geohazard seismic and seabed mapping surveys conducted in July and August 2014 (Smultea
et al.,
2014). Frouin-Mouy
et al.
(2016) conducted acoustic monitoring in Foggy Island Bay from early July to late September 2014, and detected pinniped vocalizations on 10 days via the nearshore recorder and on 66 days via the recorder farther offshore. Although the majority of these detections were unidentified pinnipeds, bearded seal vocalizations were positively identified on two days (Frouin-Mouy
et al.,
2016).
Bearded seals are an important resource for Alaska Native subsistence hunters. Approximately 64 Alaska Native communities in western and northern Alaska, from Bristol Bay to the Beaufort Sea, regularly harvest ice seals (Ice Seal Committee, 2016). However, during 2009-2013, only 12 of 64 coastal communities were surveyed for bearded seals; and, of those communities, only 6 were surveyed for two or more consecutive years (Ice Seal Committee, 2016). Based on the harvest data from these 12 communities (Table 2), a minimum estimate of the average annual harvest of bearded seals in 2009-2013 is 390 seals. Harvest surveys are designed to estimate harvest within the surveyed community, but because of differences in seal availability, cultural hunting practices, and environmental
conditions, extrapolating harvest numbers beyond that community is not appropriate (Muto
et al.,
2016).
Of the 22 federally-regulated U.S. commercial fisheries in Alaska monitored for incidental mortality and serious injury by fisheries observers, 12 fisheries could potentially interact with bearded seals. During 2010-2014, incidental mortality and serious injury of bearded seals occurred in three fisheries: The Bering Sea/Aleutian Islands pollock trawl, Bering Sea/Aleutian Islands flatfish trawl, and Bering Sea/Aleutian Islands Pacific cod trawl fisheries (Muto
et al.,
2016). This species was also part of the aforementioned 2011-2016 UME.
Spotted Seal
Spotted seals are distributed along the continental shelf of the Bering, Chukchi, and Beaufort seas, and the Sea of Okhotsk south to the western Sea of Japan and northern Yellow Sea. Eight main areas of spotted seal breeding have been reported (Shaughnessy and Fay, 1977) and Boveng
et al.
(2009) grouped those breeding areas into three DPSs: The Bering DPS, which includes breeding areas in the Bering Sea and portions of the East Siberian, Chukchi, and Beaufort seas that may be occupied outside the breeding period; the Okhotsk DPS; and the Southern DPS, which includes spotted seals breeding in the Yellow Sea and Peter the Great Bay in the Sea of Japan. For the purposes of MMPA stock assessments, NMFS defines the Alaska stock of spotted seals to be that portion of the Bering DPS in U.S. waters.
The distribution of spotted seals is seasonally related to specific life-history events that can be broadly divided into two periods: Late-fall through spring, when whelping, nursing, breeding, and molting occur in association with the presence of sea ice on which the seals haul out, and summer through fall when seasonal sea ice has melted and most spotted seals use land for hauling out (Boveng
et al.,
2009). Spotted seals are most numerous in the Bering and Chukchi seas (Quakenbush, 1988), although small numbers do range into the Beaufort Sea during summer (Rugh
et al.,
1997; Lowry
et al.,
1998).
At Northstar, few spotted seals have been observed. A total of 12 spotted seals were positively identified near the source-vessel during open-water seismic programs in the central Alaskan Beaufort Sea, generally occurring near Northstar from 1996 to 2001 (Moulton and Lawson, 2002). The number of spotted seals observed per year ranged from zero (in 1998 and 2000) to four (in 1999).
During a seismic survey in Foggy Island Bay, PSOs recorded 18 pinniped sightings, of which one was confirmed as a spotted seal (Aerts
et al.,
2008). Spotted seals were the second most abundant seal species observed by PSOs during Hilcorp's geohazard surveys in July-August 2014 (Smultea
et al.,
2014) and in July 2015 (Cate
et al.,
2015). Given their seasonal distribution and low numbers in the nearshore waters of the central Alaskan Beaufort Sea, no spotted seals are expected in the action area during late winter and spring, but could be present in low numbers during the summer or fall.
Similar to other ice seal species, spotted seals are an important resource for Alaska Native subsistence hunters. Of the 12 communities (out of 64) surveyed during 2010-2014, the minimum annual spotted seal harvest estimates totaled across 12 out of 64 user communities surveyed ranged from 83 (in 2 communities) to 518 spotted seals (in 10 communities). Based on the harvest data from these 12 communities, a minimum estimate of the average annual harvest of spotted seals in 2010-2014 is 328 seals.
From 2011-2015, incidental mortality and serious injury of spotted seals occurred in 2 of the 22 federally-regulated U.S. commercial fisheries in Alaska monitored for incidental mortality and serious injury by fisheries observers: The Bering Sea/Aleutian Islands flatfish trawl and Bering Sea/Aleutian Islands Pacific cod longline fisheries. In 2014, there was one report of a mortality incidental to research on the Alaska stock of spotted seals, resulting in a mean annual mortality and serious injury rate of 0.2 spotted seals from this stock in 2011-2015. This species was also part of the aforementioned 2011-2016 UME.
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 and 2019) 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 (2016) 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 an exception for lower limits for low-frequency cetaceans where the result 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 estimated to occur between approximately 7 (hertz) 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):
Functional hearing is estimated to occur between approximately 50 Hz to 86 kHz; and
•
Pinnipeds in water; Otariidae (eared seals):
Functional hearing is estimated to occur between approximately 60 Hz and 39 kHz.
For more detail concerning these groups and associated frequency ranges, please see NMFS (2018) for a review of available information. Six marine mammal species (three cetacean and three phocid pinniped) have the potential to co-occur with Hilcorp's LDPI project. Of the three cetacean species that may be present, two are classified as low-frequency cetaceans (
i.e.,
all mysticete species) and one is classified as a mid-frequency cetacean (beluga whale).
Potential Effects of the Specified Activity 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
Proposed 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.
The potential impacts of the proposed LDPI on marine mammals involve both non-acoustic and acoustic effects. Potential non-acoustic effects could result from the physical presence of personnel, structures and equipment, construction or maintenance activities, and the occurrence of oil spills. The LDPI project also has the potential to result in mortality and serious injury of ringed seals via direct physical interaction on ice roads and harass (by Level A harassment and Level B harassment) cetaceans and seals via acoustic disturbance. We first discuss the effects of ice road and ice trail construction and maintenance on ringed seals with respect to direct human interaction followed by an in-depth discussion on sound and potential effects on marine mammals from acoustic disturbance. The potential for and potential impacts from both small and large oil spills are discussed in more detail later in this section; however, please note Hilcorp did not request, nor is NMFS proposing to authorize, take from oil spills.
Mortality, Serious Injury and Non-Acoustic Harassment—Ice Seals
This section discusses the potential impacts of ice road construction, use and maintenance on ringed seals, the only species likely to be encountered during this activity. Acoustic impacts from this and other activities (
e.g.,
pile driving) are provided later in the document. To assess the potential impacts from ice roads, one must understand sea ice dynamics, the influence of ice roads on sea ice, and ice seal ecology.
Sea ice is constantly moving and flexing due to winds, currents, and snow load. Sea ice grows (thickens) to its maximum in March, then begins to degrade once solar heating increases above the necessary threshold. Sea ice will thin and crack due to atmospheric pressure and temperature changes. In the absence of ice roads, sea ice is constantly cracking, deforming (creating pressure ridges and hummocks), and thickening or thinning. Ice road construction interrupts this dynamic by permanently thickening and stabilizing the sea ice for the season; however, it thins and weakens sea ice adjacent to ice roads due to weight of the ice road and use as speed and load of vehicles using the road creates pressure waves in the ice, cracking natural ice adjacent to the road (pers. comm., M. Williams, August 17, 2018). These cracks and thinned ice, occurring either naturally or adjacent to ice roads, are easily exploitable habitat for ringed seals.
As discussed in the Description of Marine Mammal section, ringed seals build lairs which are typically concentrated along pressure ridges, cracks, leads, or other surface deformations (Smith and Stirling 1975, Hammill and Smith, 1989, Furgal
et al.,
1996). To build a lair, a pregnant female will first excavate a breathing hole, most easily in cracked or thin ice. The lair will then be excavated (snow must be present for lair construction). Later in the season, basking holes may be created from collapsed lairs or new basking holes will be excavated; both of which must have breathing holes and surface access (pers. comm., M. Williams, August 17, 2018).
Williams
et al.
(2006) provides the most in-depth discussion of ringed seal use around Northstar Island, the first offshore oil and gas production facility seaward of the barrier islands in the Alaskan Beaufort Sea. Northstar is located 9.5 km from the mainland on a manmade gravel island in 12 m of water. In late 2000 and early 2001, sea ice in areas near Northstar Island where summer water depth was greater than 1.5 m was searched for ringed seal structures. At Northstar, ringed seals were documented creating and using sea ice structures (basking holes, breathing holes, or birthing lairs) within 11 to 3,500 m (36 to 11,482 ft) of Northstar infrastructure which includes ice roads, pipeline, and the island itself (Williams
et al.,
2006). Birth lairs closest to Northstar infrastructure were 882 m and 144 m (2,894 and 374 ft) from the island and ice road, respectively (Williams
et al.,
2006). Two basking holes were found within 11 and 15 m (36 and 49 ft) from the nominal centerline of a Northstar ice road and were still in use by the end of the study (Williams
et al.,
2006). Although located in deeper water outside of the barrier islands, we anticipate ringed seals would use ice around the LDPI and associated ice roads in a similar manner.
Since 1998, there have been three documented incidents of ringed seal interactions on North Slope ice roads, with one recorded mortality. On April 17, 1998, during a vibroseis on-ice seismic operation outside of the barrier islands east of Bullen Point in the eastern Beaufort Sea, a ringed seal pup was killed when its lair was destroyed by a Caterpillar tractor clearing an ice road. The lair was located on ice over water 9 m (29 ft) deep with an ice thickness of 1.3 m (4.3 ft). It was reported that an adult may have been present in the lair when it was destroyed. Crew found blood on the ice near an open hole approximately 1.3 km (0.8 mi) from the destroyed lair; this could have been from a wounded adult (MacLean, 1998). On April 24, 2018, a Tucker (a tracked vehicle used in snow conditions) traveling on a Northstar sea ice trail broke through a brine pocket. After moving the Tucker, a seal pup climbed out of the hole in the ice, but no adult was seen in the area. The seal pup remained in the area for the next day and a half. This seal was seen in an area with an estimated water depth of 6 to 7 m (20 to 24 ft) (Hilcorp, 2018b). The third reported incident occurred on April 28, 2018, when a contractor performing routine maintenance activities to relocate metal plates beneath the surface of the ice road from Oliktok Point to Spy Island Drill site spotted a ringed seal pup next to what may have been a lair site. No adult was observed in the area. The pup appeared to be acting normally and was seen going in and out of the opening several times (Eni, 2018).
Overall, NMFS does not anticipate the potential for mortality or serious injury of ringed seals to be high given there has been only one documented mortality over 25 years of ice road construction in the Arctic. However, the potential does exist; therefore, we are including a small amount of mortality or serious injury (n = 2) in this proposed rule over the five-year life of the regulations. To mitigate this risk, NMFS and Hilcorp have developed a number of best management practices (BMPs) aimed at reducing the potential of disturbing (
e.g.,
crushing) ice seal structures on ice roads (see Proposed Mitigation and Monitoring).
Potential Acoustic Impacts—Level A Harassment and Level B Harassment
In the following discussion, we provide general background information
on sound before considering potential effects to marine mammals from sound produced by construction and operation of the LDPI.
Description of Sound Sources
This section contains a brief technical background on sound, on the characteristics of certain sound types, and on metrics used in this proposal inasmuch 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. For general information on sound and its interaction with the marine environment, please see,
e.g.,
Au and Hastings (2008); Richardson
et al.
(1995); Urick (1983).
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 decibel (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 (μPa)), 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 μPa), while the received level is the SPL at the listener's position (referenced to 1 μPa).
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 μPa
2
-s) represents the total energy in a stated frequency band over a stated time interval or event, and considers both intensity and duration of exposure. The per-pulse SEL is calculated over the time window containing the entire pulse (
i.e.,
100 percent of the acoustic energy). SEL is a cumulative metric; it can be accumulated over a single pulse, or calculated over periods containing multiple pulses. Cumulative SEL represents the total energy accumulated by a receiver over a defined time window or during an event. Peak sound pressure (also referred to as zero-to-peak sound pressure or 0-pk) 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.
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 sound produced by the pile driving activity 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, which is defined as environmental background sound levels lacking a single source or point (Richardson
et al.,
1995). 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 wind and waves, which are a main source of naturally occurring ambient sound for frequencies between 200 Hz and 50 kHz (Mitson, 1995). In general, ambient sound levels tend to increase with increasing wind speed and wave height. Precipitation can become an important component of total sound at frequencies above 500 Hz, and possibly down to 100 Hz during quiet times. Marine mammals can contribute significantly to ambient sound levels, as can some fish and snapping shrimp. The frequency band for biological contributions is from approximately 12 Hz to over 100 kHz. Sources of ambient sound related to human activity include transportation (surface vessels), dredging and construction, oil and gas drilling and production, geophysical surveys, sonar, and explosions. Vessel noise typically dominates the total 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.
The sum of the various natural and anthropogenic sound sources that comprise ambient sound at any given location and time 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 decibels (dB) from day to day (Richardson
et al.,
1995). The result is that, depending on the source type and its intensity, sound from the specified activity may be a negligible addition to the local environment or could form a distinctive signal that may affect marine mammals.
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). See Southall
et al.
(2007) for an in-depth discussion of these concepts. The distinction between these two sound types is not always obvious, as certain signals share properties of both pulsed and non-pulsed sounds. A signal near a source could be categorized as a pulse, but due to propagation effects as it moves farther from the source, the signal duration becomes longer (
e.g.,
Greene and Richardson, 1988).
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 intermittent (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. The duration of such sounds, as received at a distance, can be greatly extended in a highly reverberant environment.
The impulsive sound generated by impact hammers is characterized by rapid rise times and high peak levels. Vibratory hammers produce non-impulsive, continuous noise at levels significantly lower than those produced by impact hammers. Rise time is slower, reducing the probability and severity of injury, and sound energy is distributed over a greater amount of time (
e.g.,
Nedwell and Edwards, 2002; Carlson
et al.,
2005).
Acoustic Effects
We previously provided general background information on marine mammal hearing (see “Description of Marine Mammals in the Area of the Specified Activity”). Here, we discuss the potential effects of sound on marine mammals.
Potential Effects of Underwater Sound
—Note that, in the following discussion, we refer in many cases to a 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; Götz
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 pile driving.
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.
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 construction and operational activities associated with the LDPI do not involve the use of devices such as explosives or mid-frequency tactical sonar that are associated with these types of effects.
Auditory Threshold Shifts
NMFS defines threshold shift (TS) as a change, usually an increase, in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS, 2018). The amount of threshold shift is customarily expressed in decibels (ANSI, 1995). Threshold shift can be permanent (PTS) or temporary (TTS). As described in NMFS (2018), there are numerous factors to consider when examining the consequence of TS, including, but not limited to, the signal temporal pattern (
e.g.,
impulsive or non-impulsive), likelihood an individual would be exposed for a long enough duration or to a high enough level to induce a TS, the magnitude of the TS, time to recovery (seconds to minutes or hours to days), the frequency range of the exposure (
i.e.,
spectral content), the hearing and vocalization frequency range of the exposed species relative to the signal's frequency spectrum (
i.e.,
how animal uses sound within the frequency band of the signal;
e.g.,
Kastelein
et al.,
2014b), and their overlap (
e.g.,
spatial, temporal, and spectral).
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, and there is no PTS data for cetaceans, but such relationships are assumed to be similar to those in humans and other terrestrial mammals. PTS typically occurs at exposure levels at least several decibels above (a 40-dB threshold shift approximates PTS onset;
e.g.,
Kryter
et al.,
1966; Miller, 1974) that inducing 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 impact pile driving 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 thresholds are 15 to 20 dB higher than TTS cumulative sound exposure level thresholds (Southall
et al.,
2007). Given the higher level of sound or longer exposure duration necessary to cause PTS as compared with TTS, it is considerably less likely that PTS could occur.
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.
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 three 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 NMFS (2018).
NMFS defines TTS as “a temporary, reversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level” (NMFS, 2016). A TTS of 6 dB is considered the minimum threshold shift clearly larger than any day-to-day or session-to-session variation in a subject's normal hearing ability (Schlundt
et al.,
2000; Finneran
et al.,
2000; Finneran
et al.,
2002, as reviewed in Southall
et al.,
2007 for a review). TTS can last from minutes or hours to days (
i.e.,
there is recovery), occur in specific frequency ranges (
i.e.,
an animal might only have a temporary loss of hearing sensitivity between the frequencies of 1 and 10 kHz)), and can be of varying amounts (for example, an animal's hearing sensitivity might be temporarily reduced by only 6 dB or reduced by 30 dB). Currently, TTS measurements exist for only four species of cetaceans (bottlenose dolphins, belugas, harbor porpoises, and Yangtze finless porpoise) and three species of pinnipeds (Northern elephant seal, harbor seal, and California sea lion). These TTS measurements are from a limited number of individuals within these species.
Depending on the degree (elevation of threshold in dB), duration (
i.e.,
recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious (similar to those discussed in auditory masking, below). For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that takes place during a time when the animal is traveling through the open ocean, where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during time when communication is critical for successful mother/calf interactions could have more serious impacts. We note that reduced hearing sensitivity as a simple function of aging has been observed in marine mammals, as well as humans and other taxa (Southall
et al.,
2007), so we can infer that strategies exist for coping with this condition to some degree, though likely not without cost.
Behavioral Effects
—Behavioral disturbance from elevated noise exposure 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). 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; Finneran
et al.,
2003). Observed responses of wild marine mammals to loud pulsed sound sources (typically 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 low-frequency airgun source vessels with no apparent discomfort or obvious behavioral change (
e.g.,
Barkaszi
et al.,
2012), indicating the importance of frequency output in relation to the species' hearing sensitivity.
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; Costa
et al.,
2003; Ng and Leung, 2003; Nowacek
et al.;
2004; Goldbogen
et al.,
2013a, 2013b). 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 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 would require 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.
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; Gailey
et al.,
2016).
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; 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).
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 airgun surveys (Malme
et al.,
1984). Avoidance may be short-term, with animals returning to the area once the noise has ceased (
e.g.,
Bowles
et al.,
1994; Goold, 1996; Stone
et al.,
2000; Morton and Symonds, 2002; Gailey
et al.,
2007). Longer-term displacement is possible, however, which may lead to changes in abundance or distribution patterns of the affected species in the affected region if habituation to the presence of the sound does not occur (
e.g.,
Blackwell
et al.,
2004; Bejder
et al.,
2006; Teilmann
et al.,
2006).
A flight response is a dramatic change in normal movement to a directed and rapid movement away from the perceived location of a sound source. The flight response differs from other avoidance responses in the intensity of the response (
e.g.,
directed movement, rate of travel). Relatively little information on flight responses of marine mammals to anthropogenic signals 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; Fritz
et al.,
2002; 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.
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 would not pose serious fitness consequences. However, when an animal does not have sufficient energy reserves to satisfy the energetic costs of a stress response, energy resources must be diverted from other functions. This state of distress will last until the animal replenishes its energetic reserves sufficient to restore normal function.
Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses are well-studied through controlled experiments and for both laboratory and free-ranging animals (
e.g.,
Holberton
et al.,
1996; Hood
et al.,
1998; Jessop
et al.,
2003; Krausman
et al.,
2004; Lankford
et al.,
2005). Stress responses due to exposure to anthropogenic sounds or other stressors and their effects on marine mammals have also been reviewed (Fair and Becker, 2000; Romano
et al.,
2002b) and, more rarely, studied in wild populations (
e.g.,
Romano
et al.,
2002a). For example, Rolland
et al.
(2012) found that noise reduction from reduced ship traffic in the Bay of Fundy was associated with decreased stress in North Atlantic right whales. 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).
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.,
2000; Foote
et al.,
2004; Parks
et al.,
2007; Di Iorio and Clark, 2009; 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.
Potential Effects of Hilcorp's Activity
—As described previously (see “Description of the Specified Activity”), Hilcorp proposes to build ice roads, install a pipeline, construct and operate a gravel island using impact and vibratory pile driving, and drill for oil in Foggy Island Bay. These activities would occur under ice and open water conditions (with the exception of ice roads). These activities have the potential to harass marine mammals from acoustic disturbance (all species) and via human disturbance/presence on ice (ice seals). There is also potential for ice seals, specifically ringed seals, to be killed in the event a lair is crushed during ice road construction and maintenance in undisturbed areas after March 1, annually.
NMFS analyzed the potential effects of oil and gas activities, including construction of a gravel island and associated infrastructure, in its 2016 EIS on the Effects of Oil and Gas Activities in the Arctic Ocean (NMFS, 2016; available at
https://www.fisheries.noaa.gov/resource/document/effects-oil-and-gas-activities-arctic-ocean-final-environmental-impact
). Although that document focuses on seismic exploration, there is a wealth of information in that document on marine mammal impacts from anthropogenic noise. More specific to the proposed project, BOEM provides a more detailed analysis on the potential impacts of the Liberty LDPI in its' EIS on the Liberty Development and Production Plan, Beaufort Sea, Alaska, on which NMFS was a cooperating agency (BOEM, 2018; available at
https://www.boem.gov/Hilcorp-Liberty/
). We refer to those documents, specifically Chapter 4 of each of those documents, as a comprehensive impact assessment but provide a summary and complimentary analysis here.
The effects of pile driving on marine mammals are dependent on several factors, including the size, type, and depth of the animal; the depth, intensity, and duration of the pile driving sound; the depth of the water column; the substrate of the habitat; the standoff distance between the pile and the animal; and the sound propagation properties of the environment. With both types of pile driving, it is likely that the onset of pile driving could result in temporary, short term changes in an animal's typical behavioral patterns and/or avoidance of the affected area. These behavioral changes may include (as summarized in Richardson
et al.,
1995): Changing durations of surfacing and dives, number of blows per surfacing, or moving direction and/or speed; reduced/increased vocal activities; changing/cessation of certain behavioral activities (such as socializing or feeding); visible startle response or aggressive behavior (such as tail/fluke slapping or jaw clapping); avoidance of areas where sound sources are located; and/or flight responses.
For all noise-related activities, bowhead and gray whales are not anticipated to be exposed to noise above NMFS harassment threshold often. As previously described, Hilcorp aims to conduct all pile driving during the ice-covered season, as was done at Northstar; however, they are allowing for unforeseen scheduling delays. Bowheads are not present near LDPI during the winter and are not normally found in the development area during mid-summer (July through mid-August) when the whales are further east in the Canadian Beaufort. Therefore there are no impacts on foraging habitat for bowhead whales during mid-summer. Starting in late August and continuing until late October, bowheads may be exposed to sounds from the proposed activities at LDPI or may encounter vessel traffic to and from the island. It is unlikely that any whales would be displaced from sounds generated by activities at the LDPI due to their distance from the offshore migrating whales, and the effects of buffering from the barrier islands. Any displacement would be subtle and involve no more than a small proportion of the passing bowheads, likely less than that found at Northstar (Richardson, 2003, 2004; Mcdonald
et al.,
2012). This is due to the baffling-effect of the barrier island between the construction activity and the main migratory pathway of bowhead whales. Moreover, mitigation such as avoiding pile driving during the fall bowhead whale hunt further reduces potential for harassment as whales are migrating offshore.
Ongoing activities such as drilling may also harass marine mammals; however, drilling sounds from artificial islands are relatively low. As summarized in Richardson
et al.
(1995), beluga whales (the cetacean most likely to occur in Foggy Island Bay) are often observed near drillsites within 100 to 150 m (328.1 to 492.1 ft) from artificial islands. Drilling operations at Northstar facility during the open-water season resulted in brief, minor localized effects on ringed seals with no consequences to ringed seal populations (Richardson and Williams, 2004). Adult ringed seals seem to tolerate drilling activities. Brewer
et al.
(1993) noted ringed seals were the most common marine mammal sighted and did not seem to be disturbed by drilling operations at the Kuvlum 1 project in the Beaufort Sea. Southall
et al.
(2007) reviewed literature describing responses of pinnipeds to continuous sound and reported that the limited data suggest exposures between ~90 and 140 dB re 1 μPa generally do not appear to induce strong behavioral responses in pinnipeds exposed to continuous sounds in water. Hilcorp will conduct acoustic monitoring during drilling to determine if future incidental take authorizations are warranted from LDPI operation.
The biological significance of many of these behavioral disturbances is difficult to predict, especially if the detected disturbances appear minor. However, the consequences of behavioral modification could be expected to be biologically significant if the change affects growth, survival, or reproduction. Significant behavioral modifications that could lead to effects on growth, survival, or reproduction, such as drastic changes in diving/surfacing patterns or significant habitat abandonment are extremely unlikely in this area (
i.e.,
shallow waters in modified industrial areas).
The onset of behavioral disturbance from anthropogenic sound depends on both external factors (characteristics of sound sources and their paths) and the specific characteristics of the receiving animals (hearing, motivation, experience, demography) and is difficult to predict (Southall
et al.,
2007).
Whether impact or vibratory driving, sound sources would be active for relatively short durations, with relation to the durations animals use sound (either emitting or receiving) on a daily basis, and over a small spatial scale
relative to marine mammal ranges. Therefore, the potential impacts from masking are limited in both time and space. Further, the frequencies output of pile driving are low relative to the range of frequencies used by most species for vital life functions such as communication or foraging. In summary, we expect some masking to occur; however, the biological impacts of any potential masking are anticipated to be negligible. Finally, any masking that might rise to Level B harassment under the MMPA would occur concurrently within the zones of behavioral harassment already estimated for vibratory and impact pile driving, and which have already been taken into account in the exposure analysis.
Oil Spills
During the life of the proposed regulations, Hilcorp would be actively drilling for crude oil in Foggy Island Bay and transporting that oil via a single-phase subsea pipe-in-pipe pipeline from the LDPI to shore, where an aboveground pipeline will transport crude to the existing Badami pipeline. From there, crude will be transported to the Endicott Sales Oil Pipeline, which ties into Pump Station 1 of the TransAlaska Pipeline System (TAPS) for eventual delivery to a refinery. Whenever oil is being extracted or transported, there is potential for a spill. Accidental oil spills have a varying potential to occur and with varying impacts on marine mammals. For example, if a spill or pipeline leak occurs during the winter, oil would be trapped by the ice. However, response may be more difficult due in part to the presence of ice. If a spill or leak occurs during the open-water season, oil may disperse more widely; however, response time may be more prompt. Spills may also be large or small. Small spills are defined as spills of less than 1,000 barrels (bbls), and a large spill is greater than 1,000 bbls. For reference, 1 bbl equates to 42 gallons.
Based on BOEM's oil spill analyses in its EIS, the only sized spills that are reasonably likely to occur in association with the proposed action are small spills (<1,000 bbls) (BOEM, 2017a). Small spills, although accidental, occur during oil and gas activities with generally routine frequency and are considered likely to occur during development, production, and/or decommissioning activities associated with the proposed action. BOEM estimates about 70 small spills, most of which would be less than 10 bbls, would occur over the life of the Liberty Project. Small crude oil spills would not likely occur before drilling operations begin. Small refined oil spills may occur during development, production, and decommissioning. The majority of small spills are likely to occur during the approximate 22-year production period, which is an average of about 3 spills per year.
The majority of small spills would be contained on the proposed LDPI or landfast ice (during winter). BOEM anticipates that small refined spills that reach the open water would be contained by booms or absorbent pads; these small spills would also evaporate and disperse within hours to a few days. A 3 bbl refined oil spill during summer is anticipated to evaporate and disperse within 24 hours, and a 200 bbl refined oil spill during summer is anticipated to evaporate and disperse within 3 days (BOEM, 2017a).
A large spill is a statistically unlikely event. The average number of large spills for the proposed action was calculated by multiplying the spill rate (Bercha International Inc., 2016; BOEM, 2017a), by the estimated barrels produced (0.11779 bbl or 117.79 Million Barrels). By adding the mean number of large spills from the proposed LDPI and wells (~0.0043) and from pipelines (~0.0024), a mean total of 0.0067 large spills were calculated for the proposed action. Based on the mean spill number, a Poisson distribution indicates there is a 99.33 percent chance that no large spill occurs over the development and production phases of the project, and a 0.67 percent chance of one or more large spills occurring over the same period. The statistical distribution of large spills and gas releases shows that it is much more likely that no large spills or releases occur than that one or more occur over the life of the project. However, a large spill has the potential to seriously harm ESA-listed species and their environment. Assuming one large spill occurs instead of zero allows BOEM to more fully estimate and describe potential environmental effects (BOEM, 2017a).
Hilcorp is currently developing its oil spill response plan in coordination with the Bureau of Safety and Environmental Enforcement (BSEE) who must approve the plan. BSEE oversees oil spill planning and preparedness for oil and gas exploration, development, and production facilities in both state and Federal offshore waters of the United States. NMFS provided BSEE with its recommended marine mammal oil spill response protocols available at
https://www.fisheries.noaa.gov/resource/document/pinniped-and-cetacean-oil-spill-response-guidelines.
NMFS has provided BSEE with recommended marine mammal protocols should a spill occur. BSEE has indicated NMFS will have opportunity to provide comments on Hilcorp's plan during a Federal agency public comment period. As noted above, Hilcorp did not request, and NMFS is not proposing to authorize, take of marine mammals incidental to oil spills. NMFS does not authorize incidental take from oil spills under section 101(a)(5)(A) of the MMPA in general, and oil spills are not part of the specified activity in this case.
Cetaceans
While direct mortality of cetaceans is unlikely, exposure to spilled oil could lead to skin irritation, baleen fouling (which might reduce feeding efficiency), respiratory distress from inhalation of hydrocarbon vapors, consumption of some contaminated prey items, and temporary displacement from contaminated feeding areas. Geraci and St. Aubin (1990) summarize effects of oil on marine mammals, and Bratton
et al.
(1993) provides a synthesis of knowledge of oil effects on bowhead whales. The number of whales that might be contacted by a spill would depend on the size, timing, and duration of the spill. Whales may not avoid oil spills, and some have been observed feeding within oil slicks (Goodale
et al.,
1981).
The potential effects on cetaceans are expected to be less than those on seals (described later in this section of the document). Cetaceans tend to occur well offshore where cleanup activities (in the open-water season) are unlikely to be as concentrated. Also, cetaceans are transient and, during the majority of the year, absent from the area. Further, drilling would be postponed during the bowhead whale hunt every fall; therefore, the risk to cetaceans during this time, when marine mammal presence and subsistence use is high, has been fully mitigated.
Pinnipeds
Ringed, bearded, and spotted seals are present in open-water areas during summer and early autumn, and ringed seals remain in the area through the ice-covered season. Therefore, an oil spill from LDPI or its pipeline could affect seals. Any oil spilled under the ice also has the potential to directly contact seals. The most relevant data of pinnipeds exposed to oil is from the Exxon Valdez oil spill (EVOS).
The largest documented impact of a spill, prior to the EVOS, was on young seals in January in the Gulf of St. Lawrence (St. Aubin, 1990). Intensive and long-term studies were conducted after the EVOS in Alaska. There may
have been a long-term decline of 36 percent in numbers of molting harbor seals at oiled haulout sites in Prince William Sound following EVOS (Frost
et al.,
1994a). However, in a reanalysis of those data and additional years of surveys, along with an examination of assumptions and biases associated with the original data, Hoover-Miller
et al.
(2001) concluded that the EVOS effect had been overestimated. Harbor seal pup mortality at oiled beaches was 23% to 26%, which may have been higher than natural mortality, although no baseline data for pup mortality existed prior to EVOS (Frost
et al.,
1994a).
Adult seals rely on a layer of blubber for insulation, and oiling of the external surface does not appear to have adverse thermoregulatory effects (Kooyman
et al.,
1976, 1977; St. Aubin, 1990). However, newborn seal pups rely on their fur for insulation. Newborn ringed seal pups in lairs on the ice could be contaminated through contact with oiled mothers. There is the potential that newborn ringed seal pups that were contaminated with oil could die from hypothermia. Further, contact with oil on the external surfaces can potentially cause increased stress and irritation of the eyes of ringed seals (Geraci and Smith, 1976; St. Aubin, 1990). These effects seemed to be temporary and reversible, but continued exposure of eyes to oil could cause permanent damage (St. Aubin, 1990). Corneal ulcers and abrasions, conjunctivitis, and swollen nictitating membranes were observed in captive ringed seals placed in crude oil-covered water (Geraci and Smith, 1976), and in seals in the Antarctic after an oil spill (Lillie, 1954).
Marine mammals can ingest oil if their food is contaminated. Oil can also be absorbed through the respiratory tract (Geraci and Smith, 1976; Engelhardt
et al.,
1977). Some of the ingested oil is voided in vomit or feces but some is absorbed and could cause toxic effects (Engelhardt, 1981). When returned to clean water, contaminated animals can depurate this internal oil (Engelhardt, 1978, 1982, 1985). In addition, seals exposed to an oil spill are unlikely to ingest enough oil to cause serious internal damage (Geraci and St. Aubin, 1980, 1982).
Since ringed seals are found year-round in the U.S. Beaufort Sea and more specifically in the project area, an oil spill at any time of year could potentially have effects on ringed seals. However, they are more widely dispersed during the open-water season. Spotted seals are unlikely to be found in the project area during late winter and spring. Therefore, they are more likely to be affected by a spill in the summer or fall seasons. Bearded seals typically overwinter south of the Beaufort Sea. However, some have been reported around Northstar during early spring (Moulton
et al.,
2003b).
Oil Spill Cleanup Activities
Oil spill cleanup activities could increase disturbance effects on either whales or seals, causing temporary disruption and possible displacement (BOEM, 2018). General issues related to oil spill cleanup activities are discussed earlier in this section for cetaceans. In the event of a large spill contacting and extensively oiling coastal habitats, the presence of response staff, equipment, and the many aircraft involved in the cleanup could (depending on the time of the spill and the cleanup) potentially displace seals. If extensive cleanup operations occur in the spring, they could cause increased stress and reduced pup survival of ringed seals. Oil spill cleanup activity could exacerbate and increase disturbance effects on subsistence species, cause localized displacement of subsistence species, and alter or reduce access to those species by hunters. On the other hand, the displacement of marine mammals away from oil-contaminated areas by cleanup activities would reduce the likelihood of direct contact with oil. Impacts to subsistence uses of marine mammals are discussed later in this document (see the “Impact on Availability of Affected Species or Stock for Taking for Subsistence Uses” section).
Potential Take From Oil Spills
Hilcorp did not request, and NMFS is not proposing to authorize, take of marine mammals incidental to oil spills. Should an oil spill occur and marine mammals are killed, injured, or harassed by the spill, the “taking” would be unauthorized. However, NMFS is including mitigation and reporting measures within these proposed regulations to minimize risk to marine mammals. Should an oil spill occur at the drill site and that oil enter the marine environment such that marine mammals are at risk of exposure, NMFS is proposing to include a mitigation measure that Hilcorp notify NMFS immediately and cease drilling until NMFS can assess the severity of the spill and potential impacts to marine mammals. Should the pipeline leak, crude oil transport via the pipeline would also cease immediately until the pipeline is repaired. In the case of any spill, Hilcorp would immediately initiate communication and response protocol per its Oil Spill Response Plan. Finally, Hilcorp must maintain the frequency of oil spill response training at no less than one two hour session per week.
Anticipated Effects on Marine Mammal Habitat
The footprint of the LPDI would result in permanent impacts to habitats used directly by marine mammals; however, the footprint is minimal compared to available habitat within Foggy Island Bay and, further, few cetaceans use Foggy Island Bay. BOEM has also required mitigation designed to reduce impacts to marine mammal habitat, including water quality and habitat disturbance. For example, initial island construction (fill placement phase) and pipeline installation/backfill will occur in winter when fewer fish species are present and when water currents are low, which will reduce total suspended solids (TSS) distribution. In addition, island armoring will serve to reduce erosion and the spread of silt or gravel over potential prey habitat. However, increased turbidity and suspended solids resulting from artificial island construction or exploratory drilling discharges could have adverse impacts on water quality and, if increases persisted for extended periods of time; these impacts would be localized but could be long term (NOAA, 2016). If oil and gas industry operators comply with the U.S. Environmental Protection Agency's Clean Water Act requirements, then elevations in turbidity and concentrations of total suspended solids resulting from exploratory drilling activity would not result in unreasonable degradation of the marine environment (NOAA, 2016).
The proposed activities could also affect acoustic habitat (see Auditory Masking discussion above), but meaningful impacts are unlikely given the low usage of the area by marine mammals and limited pile driving during open-water conditions (approximately 2 weeks). There are no known foraging hotspots, or habitats of significant biological importance to marine mammals present in the marine waters in Foggy Island Bay. Migratory pathways for cetaceans exist outside the McClure Island group; however, the majority of noise from the project would be confined to Foggy Island Bay with low levels potentially propagating outside of but close to the McClure Islands during vibratory pile driving only (see Figure 5 in Appendix A of Hilcorp's application). In addition, pile driving would not occur during the fall bowhead whale migration (see Proposed Mitigation section); therefore, no impacts to migratory habitats during use is anticipated during this time period.
Effects to Prey
—Sound may affect marine mammals through impacts on the abundance, behavior, or distribution of prey species (
e.g.,
crustaceans, cephalopods, fish, zooplankton). Marine mammal prey varies by species, season, and location and, for some, is not well documented. Here, we describe studies regarding the effects of noise on known marine mammal prey.
Fish utilize the soundscape and components of sound in their environment to perform important functions such as foraging, predator avoidance, mating, and spawning (
e.g.,
Zelick
et al.,
1999; Fay, 2009). Depending on their hearing anatomy and peripheral sensory structures, which vary among species, fishes hear sounds using pressure and particle motion sensitivity capabilities and detect the motion of surrounding water (Fay
et al.,
2008). The potential effects of noise on fishes depends on the overlapping frequency range, distance from the sound source, water depth of exposure, and species-specific hearing sensitivity, anatomy, and physiology. Key impacts to fishes may include behavioral responses, hearing damage, barotrauma (pressure-related injuries), and mortality.
Fish react to sounds which are especially strong and/or intermittent low-frequency sounds, and behavioral responses such as flight or avoidance are the most likely effects. Short duration, sharp sounds can cause overt or subtle changes in fish behavior and local distribution. The reaction of fish to noise depends on the physiological state of the fish, past exposures, motivation (
e.g.,
feeding, spawning, migration), and other environmental factors. 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 pile driving on fish, although several are based on studies in support of large, multiyear bridge construction projects (
e.g.,
Scholik and Yan, 2001, 2002; Popper and Hastings, 2009). Several studies have demonstrated that impulse 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). However, some studies have shown no or slight reaction to impulse sounds (
e.g.,
Pena
et al.,
2013; Wardle
et al.,
2001; Jorgenson and Gyselman, 2009). More commonly, though, the impacts of noise on fish are temporary.
SPLs of sufficient strength have been known to cause injury to fish and fish mortality. However, in most fish species, hair cells in the ear continuously regenerate and loss of auditory function likely is restored when damaged cells are replaced with new cells. Halvorsen
et al.
(2012a) showed that a TTS of 4-6 dB was recoverable within 24 hours for one species. Impacts would be most severe when the individual fish is close to the source and when the duration of exposure is long. Injury caused by barotrauma can range from slight to severe and can cause death, and is most likely to occur in fish with swim bladders. Barotrauma injuries have been documented during controlled exposure to impact pile driving (Halvorsen
et al.,
2012b; Casper
et al.,
2013).
The most likely impact to fish from pile driving activities at the project areas would be temporary behavioral avoidance of the area. The duration of fish avoidance of an area after pile driving stops is unknown, but a rapid return to normal recruitment, distribution and behavior is anticipated. In general, impacts to marine mammal prey species are expected to be minor and temporary due to the expected short daily duration of individual pile driving events and the relatively small areas being affected.
The area likely impacted by the activities is relatively small compared to the available habitat in inland waters in the region. Any behavioral avoidance by fish of the disturbed area would still leave significantly large areas of fish and marine mammal foraging habitat in the nearby vicinity. As described in the preceding, the potential for the LDPI to affect the availability of prey to marine mammals or to meaningfully impact the quality of physical or acoustic habitat is considered to be insignificant.
Estimated Take
This section provides an estimate of the number of incidental takes proposed for authorization through this proposed rule, which will inform both NMFS' consideration of “small numbers” and the negligible impact determination.
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 would primarily be by Level B harassment, as use of pile hammers, drill rigs, and ice-based equipment (
e.g.,
augers, trucks) have 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 during pile driving. The proposed mitigation and monitoring measures are expected to minimize the severity of such taking to the extent practicable.
No mortality or serious injury is anticipated as a result of exposure to acoustic sources; however, mortality and serious injury of ringed seals may occur from ice road construction, use, and maintenance conducted after March 1, annually. Below we describe how we estimated mortality and serious injury from ice road work followed by a detailed acoustic harassment estimation method.
Mortality/Serious Injury (Ice Seals)
The only species with the potential to incur serious injury or mortality during the proposed project are ringed seals during ice road construction, use, and maintenance. Other ice seal species are not known to use ice roads within the action area. As described in the Description of Marine Mammals section, pregnant ringed seals establish lairs in shorefast sea ice beginning in early March where pups are born and nursed throughout spring (March through May).
As described in the
Potential Effects of the Specified Activity on Marine Mammals and Their Habitat
section above, there have been only three documented interactions with ringed seals despite over 20 years of ice road construction on the North Slope; one mortality in 1998 and two non-lethal interactions in 2018. All three animals involved were seal pups in or near their lairs. The two recent interactions in 2018 led NMFS to work with the companies involved in the interactions, including Hilcorp, to better understand the circumstances behind the interactions and to develop a list of BMPs designed to avoid and minimize potential harassment. Hilcorp has adopted these BMPs (see
Proposed Mitigation and Monitoring
section); however, the potential for mortality remains, albeit low. Because lairs can include both a pup and its mother, but interactions with ringed seals are relatively uncommon, NMFS is proposing to authorize the taking, by mortality or serious injury, of two ringed seals over the course of five years of ice road construction.
Acoustic Harassment
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 proposed 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 would be reasonably expected to be behaviorally harassed (equated to Level B harassment) or to incur PTS of some degree (equated to Level A harassment).
Level B Harassment 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 (
e.g.,
hearing, motivation, experience, demography, behavioral context) and can be difficult to predict (Southall
et al.,
2007, Ellison
et al.,
2012). Based on what the available science indicates 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 Level B harassment. NMFS predicts that marine mammals are likely to be harassed in a manner we consider Level B harassment when exposed to underwater anthropogenic noise above received levels of 120 dB re 1 μPa (rms) for continuous (
e.g.,
vibratory pile-driving, drilling) and above 160 dB re 1 μPa (rms) for non-explosive impulsive (
e.g.,
seismic airguns) or intermittent (
e.g.,
scientific sonar) sources.
Hilcorp's Liberty Project includes the use of continuous, non-impulsive (vibratory pile driving, drilling, auguring) and intermittent, impulsive (impact pile driving) sources, and therefore the 120 and 160 dB re 1 μPa (rms) thresholds 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 proposed activity includes the use of impulsive (
e.g.,
impact pile driving) and non-impulsive (
e.g.,
vibratory pile driving, slope shaping, trenching) sources.
These thresholds are provided in Table 3. The references, analysis, and methodology used in the development of the thresholds are described in NMFS 2018 Technical Guidance, which may be accessed at
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance.
Table 3—Thresholds Identifying the Onset of Permanent Threshold Shift
Hearing Group
PTS onset acoustic thresholds *
(received level)
Impulsive
Non-impulsive
Low-Frequency (LF) Cetaceans
Cell 1:
L
pk,flat
: 219 dB;
L
E,LF,24h
: 183 dB
Cell 2:
L
E,LF,24h
: 199 dB.
Mid-Frequency (MF) Cetaceans
Cell 3:
L
pk,flat
: 230 dB;
L
E,MF,24h
: 185 dB
Cell 4:
L
E,MF,24h
: 198 dB.
High-Frequency (HF) Cetaceans
Cell 5:
L
pk,flat
: 202 dB;
L
E,HF,24h
: 155 dB
Cell 6:
L
E,HF,24h
: 173 dB.
Phocid Pinnipeds (PW) (Underwater)
Cell 7:
L
pk,flat
: 218 dB;
L
E,PW,24h
: 185 dB
Cell 8:
L
E,PW,24h
: 201 dB.
Otariid Pinnipeds (OW) (Underwater)
Cell 9:
L
pk,flat
: 232 dB;
L
E,OW,24h
: 203 dB
Cell 10:
L
E,OW,24h
: 219 dB.
* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating PTS onset. If a non-impulsive sound has the potential to exceed the peak sound pressure level thresholds associated with impulsive sounds, these thresholds should also be considered.
Note:
Peak sound pressure (
L
pk
) has a refere
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