Taking and Importing Marine Mammals; Taking Marine Mammals Incidental to Operation of Offshore Oil and Gas Facilities in the U.S. Beaufort Sea, 39706-39747 [2011-16327]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 76, Number 129 (Wednesday, July 6, 2011)]
[Proposed Rules]
[Pages 39706-39747]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-16327]



[[Page 39705]]

Vol. 76

Wednesday,

No. 129

July 6, 2011

Part V





Department of Commerce





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National Oceanic and Atmospheric Administration





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50 CFR Part 217





Taking and Importing Marine Mammals; Taking Marine Mammals Incidental 
to Operation of Offshore Oil and Gas Facilities in the U.S. Beaufort 
Sea; Proposed Rule

Federal Register / Vol. 76 , No. 129 / Wednesday, July 6, 2011 / 
Proposed Rules

[[Page 39706]]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 217

[Docket No. 100217096-1312-01]
RIN 0648-AY63


Taking and Importing Marine Mammals; Taking Marine Mammals 
Incidental to Operation of Offshore Oil and Gas Facilities in the U.S. 
Beaufort Sea

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

ACTION: Proposed rule; request for comments.

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SUMMARY: NMFS has received a request from BP Exploration (Alaska) Inc. 
(BP) for authorization for the take of marine mammals incidental to 
operation of offshore oil and gas facilities in the U.S. Beaufort Sea, 
Alaska, for the period 2011-2016. Pursuant to the Marine Mammal 
Protection Act (MMPA), NMFS is proposing to issue regulations to govern 
that take and requesting information, suggestions, and comments on 
these proposed regulations. These regulations, if issued, would include 
required mitigation measures to ensure the least practicable adverse 
impact on the affected marine mammal species and stocks.

DATES: Comments and information must be received no later than August 
5, 2011.

ADDRESSES: You may submit comments, identified by 0648-AY63, by any one 
of the following methods:
     Electronic Submissions: Submit all electronic public 
comments via the Federal eRulemaking Portal https://www.regulations.gov.
     Hand delivery or mailing of paper, disk, or CD-ROM 
comments should be addressed to Michael Payne, Chief, Permits, 
Conservation and Education Division, Office of Protected Resources, 
National Marine Fisheries Service, 1315 East-West Highway, Silver 
Spring, MD 20910.
    Comments regarding any aspect of the collection of information 
requirement contained in this proposed rule should be sent to NMFS via 
one of the means stated here and to the Office of Information and 
Regulatory Affairs, NEOB-10202, Office of Management and Budget (OMB), 
Attn: Desk Office, Washington, DC 20503, OIRA@omb.eop.gov.
    Instructions: All comments received are a part of the public record 
and will generally be posted to https://www.regulations.gov without 
change. All Personal Identifying Information (for example, name, 
address, etc.) voluntarily submitted by the commenter may be publicly 
accessible. Do not submit Confidential Business Information or 
otherwise sensitive or protected information.
    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, WordPerfect, or 
Adobe PDF file formats only.

FOR FURTHER INFORMATION CONTACT: Candace Nachman, Office of Protected 
Resources, NMFS, (301) 713-2289, ext. 156, or Brad Smith, Alaska 
Region, NMFS, (907) 271-3023.

SUPPLEMENTARY INFORMATION:

Availability

    A copy of BP's application may be obtained by writing to the 
address specified above (see ADDRESSES), calling the contact listed 
above (see FOR FURTHER INFORMATION CONTACT), or visiting the Internet 
at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm. To help NMFS 
process and review comments more efficiently, please use only one 
method to submit comments.

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce (Secretary) to allow, upon request, 
the incidental, but not intentional taking of marine mammals by U.S. 
citizens who engage in a specified activity (other than commercial 
fishing) during periods of not more than five consecutive years each if 
certain findings are made and regulations are issued or, if the taking 
is limited to harassment, notice of a proposed authorization is 
provided to the public for review.
    Authorization shall be granted if NMFS finds that the taking will 
have a negligible impact on the species or stock(s), will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses, and if the permissible methods of taking 
and requirements pertaining to the mitigation, monitoring and reporting 
of such taking are set forth.
    NMFS has defined ``negligible impact'' in 50 CFR 216.103 as:

    an impact resulting from the specified activity that cannot be 
reasonably expected to, and is not reasonably likely to, adversely 
affect the species or stock through effects on annual rates of 
recruitment or survival.

    Except with respect to certain activities not pertinent here, the 
MMPA defines ``harassment'' as:

Any act of pursuit, torment, or annoyance which (i) has the 
potential to injure a marine mammal or marine mammal stock in the 
wild [Level A harassment]; or (ii) has the potential to disturb a 
marine mammal or marine mammal stock in the wild by causing 
disruption of behavioral patterns, including, but not limited to, 
migration, breathing, nursing, breeding, feeding, or sheltering 
[Level B harassment].

Summary of Request

    On November 6, 2009, NMFS received an application from BP 
requesting authorization for the take of six marine mammal species 
incidental to operation of the Northstar development in the Beaufort 
Sea, Alaska, over the course of 5 years, which would necessitate the 
promulgation of new five-year regulations. Construction of Northstar 
was completed in 2001. The proposed activities for 2011-2016 include a 
continuation of drilling, production, and emergency training operations 
but no construction or activities of similar intensity to those 
conducted between 1999 and 2001. The likely or possible impacts of the 
planned continuing operations at Northstar 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. Petroleum development and associated activities in 
marine waters introduce sound into the environment, produced by island 
construction, maintenance, and drilling, as well as vehicles operating 
on the ice, vessels, aircraft, generators, production machinery, gas 
flaring, and camp operations. BP requests authorization to take 
individuals of three cetacean and three pinniped species by Level B 
Harassment. They are: Bowhead, gray, and beluga whales and ringed, 
bearded, and spotted seals. Further, BP requests authorization to take 
five individual ringed seals by injury or mortality annually over the 
course of the 5-year rule.

Description of the Specified Activity

Background on the Northstar Development Facility

    BP is currently producing oil from an offshore development in the 
Northstar Unit (see Figure 1 in BP's application). This development is 
the first in the Beaufort Sea that makes use of a subsea pipeline to 
transport oil to shore and

[[Page 39707]]

then into the Trans-Alaska Pipeline System. The Northstar facility was 
built in State of Alaska waters on the remnants of Seal Island 
approximately 6 mi (9.5 km) offshore from Point Storkersen, northwest 
of the Prudhoe Bay industrial complex, and 3 mi (5 km) seaward of the 
closest barrier island. It is located approximately 54 mi (87 km) 
northeast of Nuiqsut, an Inupiat community.
    The main facilities associated with Northstar include a gravel 
island work surface for drilling and oil production facilities and two 
pipelines connecting the island to the existing infrastructure at 
Prudhoe Bay. One pipeline transports crude oil to shore, and the second 
imports gas from Prudhoe Bay for gas injection at Northstar. Permanent 
living quarters and supporting oil production facilities are also 
located on the island.
    The construction of Northstar began in early 2000 and continued 
through 2001. BP states that activities with similar intensity to those 
that occurred during the construction phase between 2000 and 2001 are 
not planned or expected for any date within the 5-year period that 
would be governed by the proposed regulations (i.e., 2011-2016). Well 
drilling began on December 14, 2000, and oil production commenced on 
October 31, 2001. Construction and maintenance activities occurred 
annually on the protection barrier around Northstar due to ice and 
storm impacts. In August 2003, two barges made a total of 52 round-
trips to haul 30,000 cubic yards of gravel from West Dock for berm 
construction. Depending on the actual damage, repair and maintenance in 
the following years consisted of activities such as creating a moat for 
diver access, removing concrete blocks in areas that had sustained 
erosion and/or block damage, and installing a new layer of filter 
fabric. In 2008, BP installed large boulders at the NE corner of the 
barrier instead of replacing the lower concrete blocks that were 
removed during a storm.
    The planned well-drilling program for Northstar was completed in 
May 2004. Drilling activities to drill new wells, conduct well 
maintenance, and drill well side-tracks continued in 2006 (six wells), 
2007 (two wells), and 2008 (two wells). The drill rig was demobilized 
and removed from the island by barge during the 2010 open water period. 
Although future drilling is not specifically planned, drilling of 
additional wells or well work-over may be required at some time in the 
future. A more detailed description of past construction, drilling, and 
production activities at Northstar can be found in BP's application 
(see ADDRESSES).

Expected Activities in 2011-2016

    During the 5-year period from 2011-2016, BP intends to continue 
production and emergency training operations. As mentioned previously, 
drilling is not specifically planned for the 2011-2016 time period but 
may be required at some point in the future. The activities described 
next could occur at any time during the 5-year period. Table 2 in BP's 
application (see ADDRESSES) summarizes the vehicles and machinery used 
during BP's Northstar activities since the development of Northstar 
Island. Although all these activities are not planned to take place 
during the 2011-2016 operational phase, some of the equipment may be 
required to repair or replace existing structures or infrastructure on 
Northstar in the future.
(1) Transportation of Personnel, Equipment, and Supplies
    Transportation needs for the Northstar project include the ability 
to safely transport personnel, supplies, and equipment to and from the 
site during repairs or maintenance, drilling, and operations in an 
offshore environment. During proposed island renewal construction that 
may take place during the requested time period, quantities of pipes, 
vertical support members (i.e., posts that hold up terrestrial 
pipelines), gravel, and a heavy module will be transported to the site. 
Drilling operations require movement of pipe materials, chemicals, and 
other supplies to the island. During ongoing field operations, 
equipment and supplies will need to be transported to the site. All 
phases of construction, drilling, and operation require movement of 
personnel to and from the Northstar area.
    During the operations phase from 2002-2009, fewer ice roads were 
required compared to the construction phase (2000-2001). The future 
scope of ice road construction activities during ongoing production is 
expected to be similar to the post-construction period of 2002-2009. 
The locations, dimensions, and construction techniques of these ice 
roads are described in the multi-year final comprehensive report 
(Richardson [ed.], 2008). The presence of ice roads allows the use of 
standard vehicles such as pick-ups, SUVs, buses and trucks for 
transport of personnel and equipment to and from Northstar during the 
ice-covered period. Ice roads are planned to be constructed and used as 
a means of winter transportation for the duration of Northstar 
operations. The orientation of future ice roads is undetermined, but 
will not exceed the number of ice roads created during the winter of 
2000/2001.
    Barges and Alaska Clean Seas (ACS) vessels are used to transport 
personnel and equipment from the Prudhoe Bay area to Northstar during 
the open-water season, which extends from approximately mid- to late-
July through early to mid-October. Seagoing barges are used to 
transport large modules and other supplies and equipment during the 
construction period.
    Helicopter access to Northstar Island continues to be an important 
transportation option during break-up and freeze-up of the sea ice when 
wind, ice conditions, or other operational considerations prevent or 
limit hovercraft travel. Helicopters will be used for movement of 
personnel and supplies in the fall after freeze-up begins and vessel 
traffic is not possible but before ice roads have been constructed. 
Helicopters will also be used in the spring after ice roads are no 
longer safe for all-terrain vehicles (ATVs) but before enough open 
water is available for vessel traffic. Helicopters are also available 
for use at other times of year in emergency situations. Helicopters fly 
at an altitude of at least 1,000 ft (305 m), except for take-off, 
landing, and as dictated for safe aircraft operations. Designated 
flight paths are assigned to minimize potential disturbance to wildlife 
and subsistence users.
    The hovercraft is used to transport personnel and supplies during 
break-up and freeze-up periods to reduce helicopter use. BP intends to 
continue the use of the hovercraft in future years. Specifications of 
the hovercraft and sound characteristics are described in Richardson 
([ed.] 2008) and Blackwell and Greene (2005).
(2) Production Operations
    The process facilities for the Northstar project are primarily 
prefabricated sealift modules that were shipped to the island and 
installed in 2001. The operational aspects of the Northstar production 
facility include the following: Two diesel generators (designated 
emergency generators); three turbine generators for the power plant, 
operating at 50 percent duty cycle (i.e., only two will be operating at 
any one time); two high pressure turbine compressors; one low pressure 
flare; and one high pressure flare. Both flares are located on the 215 
ft (66 m) flare tower. Modules for the facility include permanent 
living quarters (i.e., housing, kitchen/dining, lavatories, medical, 
recreation, office, and laundry space), utility module (i.e., 
desalinization plant,

[[Page 39708]]

emergency power, and wastewater treatment plant), warehouse/shop 
module, communications module, diesel and potable water storage, and 
chemical storage. Operations have been continuing since oil production 
began on October 31, 2001 and are expected to continue beyond 2016.
(3) Drilling Operations
    The drilling rig and associated equipment was moved by barge to 
Northstar Island from Prudhoe Bay during the open-water season in 2000. 
Drilling began in December 2000 using power supplied by the installed 
gas line. The first well drilled was the Underground Injection Control 
well, which was commissioned for disposal of permitted muds and 
cuttings on January 26, 2001. After Northstar facilities were 
commissioned, drilling above reservoir depth resumed, while drilling 
below that depth is allowed only during the ice covered period. 
Although future drilling is not specifically planned during the 
requested time period for this proposed rule, drilling of additional 
wells or well work-over may be required at some time during 2011-2016.
(4) Pipeline Design, Inspection, and Maintenance
    The Northstar pipelines have been designed, installed, and 
monitored to assure safety and leak prevention. Pipeline monitoring and 
surveillance activities have been conducted since oil production began, 
and BP will conduct long-term monitoring of the pipeline system to 
assure design integrity and to detect any potential problems through 
the life of the Northstar development. The program will include visual 
inspections/aerial surveillance and pig (a gauging/cleaning device) 
inspections.
    The Northstar pipelines include the following measures to assure 
safety and leak prevention:
     Under the pipeline design specifications, the tops of the 
pipes are 6-8 ft (1.8-2.4 m) below the original seabed (this is 2 times 
the deepest measured ice gouge);
     The oil pipeline uses higher yield steel than required by 
design codes as applied to internal pressure (by a factor of over 2.5 
times). This adds weight and makes the pipe stronger. The 10-in (25.4-
cm) diameter Northstar oil pipeline has thicker walls than the 48-in 
(122-cm) diameter Trans-Alaska Pipeline;
     The pipelines are designed to bend without leaking in the 
event of ice keel impingement or the maximum predicted subsidence from 
permafrost thaw;
     The pipelines are coated on the outside and protected with 
anodes to prevent corrosion; and
     The shore transition is buried to protect against storms, 
ice pile-up, and coastal erosion. The shore transition valve pad is 
elevated and set back from the shoreline.
    A best-available-technology leak detection system is being used 
during operations to monitor for any potential leaks. The Northstar 
pipeline incorporates two independent, computational leak detection 
systems: (1) The Pressure Point Analysis (PPA) system, which detects a 
sudden loss of pressure in the pipeline; and (2) the mass balance leak 
detection system, which supplements the PPA. Furthermore, an 
independent hydrocarbon sensor, the LEOS leak detection system, located 
between the two pipelines, can detect hydrocarbon vapors and further 
supplements the other systems.
     Intelligent inspection pigs are used during operations to 
monitor pipe conditions and measure any changes.
     The line is constructed with no flanges, valves, or 
fittings in the subsea section to reduce the likelihood of equipment 
failure.
    During operations, BP conducts aerial forward looking infrared 
(FLIR) surveillance of the offshore and onshore pipeline corridors at 
least once per week (when conditions allow), to detect pipeline leaks. 
Pipeline isolation valves are inspected on a regular basis. In addition 
to FLIR observations/inspections, BP conducts a regular oil pipeline 
pig inspection program to assess continuing pipeline integrity. The 
LEOS Leak Detection System is used continuously to detect under-ice 
releases during the ice covered period.
    The pipelines are also monitored annually to determine any 
potential sources of damage along the pipeline route. The monitoring 
work has been conducted in two phases: (1) A helicopter-based 
reconnaissance of strudel drainage features in early June; and (2) a 
vessel-based survey program in late July and early August. During the 
vessel-based surveys, multi-beam, single-beam, and side scan sonar are 
used. These determine the locations and characteristics of ice gouges 
and strudel scour depressions in the sea bottom along the pipeline 
route and at additional selected sites where strudel drainage features 
have been observed. If strudel scour depressions are identified, 
additional gravel fill is placed in the open water season to maintain 
the sea bottom to original pipeline construction depth.
(5) Routine Repair and Maintenance
    Various routine repair and maintenance activities have occurred 
since the construction of Northstar. Examples of some of these 
activities include completion and repair of the island slope protection 
berm and well cellar retrofit repairs. Activities associated with these 
repairs or modifications are reported in the 1999-2004 final 
comprehensive report (Rodrigues and Williams, 2006) and since 2005 in 
the various Annual Reports (Rodrigues et al., 2006; Rodrigues and 
Richardson, 2007; Aerts and Rodrigues, 2008; Aerts, 2009). Some of 
these activities, such as repair of the island slope protection berm, 
were major repairs that involved the use of barges and heavy equipment, 
while others were smaller-scale repairs involving small pieces of 
equipment and hand operated tools. The berm surrounding the island is 
designed to break waves and ice movement before they contact the island 
work surface and is subjected to regular eroding action from these 
forces. The berm and sheet pile walls will require regular surveying 
and maintenance in the future. Potential repair and maintenance 
activities that are expected to occur at Northstar during the period 
2011-2016 include pile driving, traffic, gravel transport, dock 
construction and maintenance, diving and other activities similar to 
those that have occurred in the past.
(6) Emergency and Oil Spill Response Training
    Emergency and oil spill response training activities are conducted 
at various times throughout the year at Northstar. Oil spill drill 
exercises are conducted by ACS during both the ice-covered and open-
water periods. During the ice-covered periods, exercises are conducted 
for containment of oil in water and for detection of oil under ice. 
These spill drills have been conducted on mostly bottom-fast ice in an 
area 200 ft x 200 ft (61 m x 61 m) located just west of the island, 
using snow machines and ATVs. The spill drill includes the use of 
various types of equipment to cut ice slots or drill holes through the 
floating sea ice. Typically, the snow is cleared from the ice surface 
with a Bobcat loader and snow blower to allow access to the ice. Two 
portable generators are used to power light plants at the drill site. 
The locations and frequency of future spill drills or exercises will 
vary depending on the condition of the sea ice and training needs.
    ACS conducts spill response training activities during the open-
water season

[[Page 39709]]

during late July through early October. Vessels used as part of the 
training typically include Zodiacs, Kiwi Noreens, and Bay-class boats 
that range in length from 12-45 ft (3.7-13.7 m). Future exercises could 
include other vessels and equipment.
    ARKTOS amphibious emergency escape vehicles are stationed on 
Northstar Island. Each ARKTOS is capable of carrying 52 people. 
Training exercises with the ARKTOS are conducted monthly during the 
ice-covered period. ARKTOS training exercises are not conducted during 
the summer. Equipment and techniques used during oil spill response 
exercises are continually updated, and some variations relative to the 
activities described here are to be expected.
(7) Northstar Abandonment
    Detailed plans for the decommissioning of Northstar will be 
prepared near the end of field life, which will not occur during the 
period requested for these proposed regulations. For additional 
information on abandonment and decommissioning of the Northstar 
facility, refer to BP's application (see ADDRESSES).

Northstar Sound Characteristics

    During continuing production activities at Northstar, sounds and 
non-acoustic stimuli will be generated by vehicle traffic, vessel 
operations, helicopter operations, drilling, and general operations of 
oil and gas facilities (e.g., generator sounds and gas flaring). The 
sounds generated from transportation activities will be detectable 
underwater and/or in air some distance away from the area of activity. 
The distance will depend on the nature of the sound source, ambient 
noise conditions, and the sensitivity of the receptor. Take of marine 
mammals by Level B harassment incidental to the activities mentioned in 
this document could occur for the duration of these proposed 
regulations. The type and significance of the harassment is likely to 
depend on the species and activity of the animal at the time of 
reception of the stimulus, as well as the distance from the sound 
source and the level of the sound relative to ambient conditions.
(1) Construction Sounds
    Sounds associated with construction of Seal Island in 1982 were 
studied and described by Greene (1983a) and summarized in the previous 
petition for regulations submitted by BP (BPXA, 1999). Underwater and 
in-air sounds and iceborne vibrations of various activities associated 
with the final construction phases of Northstar were recorded in the 
winter of 2000-2002 (Greene et al., 2008). The main purpose of these 
measurements was to characterize the properties of island construction 
sounds and to use this information in assessing their possible impacts 
on wildlife. Activities recorded included ice augering, pumping sea 
water to flood the ice and build an ice road, a bulldozer plowing snow, 
a Ditchwitch cutting ice, trucks hauling gravel over an ice road to the 
island site, a backhoe trenching the sea bottom for a pipeline, and 
both vibratory and impact sheet pile driving (Greene et al., 2008). 
Table 5 in BP's application presents a summary of the levels of 
construction sounds and vibrations measured around the Northstar 
prospect.
    Ice road construction is difficult to separate into its individual 
components, as one or more bulldozers and several rolligons normally 
work concurrently. Of the construction activities reported, those 
related to ice road construction (bulldozers, augering and pumping) 
produced the least amount of sound, in all three media. The distance to 
median background for the strongest one-third octave bands for 
bulldozers, augering, and pumping was less than 1.24 mi (2 km) for 
underwater sounds, less than 0.62 mi (1 km) for in-air sounds, and less 
than 2.5 mi (4 km) for iceborne vibrations (see Table 5 in BP's 
application). Vibratory sheet pile driving produced the strongest 
sounds, with broadband underwater levels of 143 dB re 1 [micro]Pa at 
328 ft (100 m). Most of the sound energy was in a tone close to 25 Hz. 
Distances to background levels of underwater sounds (approximately 1.86 
mi [3 km]) were somewhat smaller than expected. Shepard et al. (2001) 
recorded sound near Northstar in April 2001 during construction and 
reported that the noisiest conditions occurred during sheet pile 
installation with a vibrating hammer. BP's estimates were 8-10 dB 
higher at 492 ft (150 m) and 5-8 dB lower at 1.24 mi (2 km) than the 
measurements by Shepard et al. (2001). Greene et al. (2008) describes 
sound levels during impact sheet pile driving. However, satisfactory 
recordings for this activity were only obtained at one station 2,395 ft 
(730 m) from the sheet pile driven into the island. The maximum peak 
pressure recorded on the hydrophone was 136.1 dB re 1 [micro]Pa and 
141.1 dB re 1 [micro]Pa on the geophone (Greene et al., 2008).
(2) Operational Sounds
    Drilling operations started in December 2000 and were the first 
sound-producing activities associated with the operational phase at 
Northstar. The four principal operations that occur during drilling are 
drilling itself, tripping (extracting and lowering the drillstring), 
cleaning, and well-logging (lowering instruments on a cable down the 
hole). Drilling activities can be categorized as non-continuous sounds, 
i.e., they contribute to Northstar sounds intermittently. Other non-
continuous sounds are those from heavy equipment operation for snow 
removal, berm maintenance, and island surface maintenance. Sounds from 
occasional movements of a ``pig'' through the pipeline may also 
propagate into the marine or nearshore environment.
    Sounds from generators, process operations (e.g., flaring, seawater 
treatment, oil processing, gas injection), and island lighting are more 
continuous and contribute to the operational sounds from Northstar. 
Drilling and operational sounds underwater, in air, and of ice-borne 
vibrations were obtained at Northstar Island and are summarized here 
and in a bit more detail in BP's application (Blackwell et al., 2004b; 
Blackwell and Greene, 2006).
    Drilling--During the ice covered seasons from 1999 to 2002, 
drilling sounds were measured and readily identifiable underwater, with 
a marked increase in received levels at 60-250 Hz and 700-1400 Hz 
relative to no-drilling times. The higher-frequency peak, which was 
distinct enough to be used as a drilling ``signature'', was clearly 
detectible 3.1 mi (5 km) from the drill rig, but had fallen to 
background values by 5.8 mi (9.4 km). Distances at which background 
levels were reached were defined as the distance beyond which broadband 
levels remained constant with increasing distance from the source. 
Sound pressure levels of island production with and without drilling 
activities measured at approximately 1,640 ft (500 m) from Northstar 
are similar, with most of the sound energy below 100 Hz. The broadband 
(10-10,000 Hz) level was approximately 2 dB higher during drilling than 
without, but relatively low in both cases (99 vs. 97 dB re 1 [micro]Pa; 
Blackwell and Greene, 2006).
    In air, drilling sounds were not distinguishable from overall 
island sounds based on spectral characteristics or on broadband levels 
(Blackwell et al., 2004b). A similar result was found for recordings 
from geophones: broadband levels of iceborne vibrations with or without 
drilling were indistinguishable (Blackwell et al., 2004b). Thus, 
airborne sounds and iceborne vibrations were not strong enough during 
drilling to have much influence on overall Northstar sound, in contrast 
to underwater

[[Page 39710]]

sounds, which were higher during drilling (Blackwell and Greene, 2006).
    Richardson et al. (1995b) summarized then-available data by stating 
that sounds associated with drilling activities vary considerably, 
depending on the nature of the ongoing operations and the type of 
drilling platform (island, ship, etc.). Underwater sound associated 
with drilling from natural barrier islands or an artificial island 
built mainly of gravel is generally weak and is inaudible at ranges 
beyond several kilometers. The results from the Northstar monitoring 
work in more recent years are generally consistent with the earlier 
evidence.
    Other Operational Sounds: Ice-covered Season--Both with and without 
drilling, underwater broadband levels recorded north of the island 
during the ice-covered season were similar with and without production 
(Blackwell et al., 2004b). Although the broadband underwater levels did 
not seem to be affected appreciably by production activities, a peak at 
125-160 Hz could be related to production. This peak was no longer 
detectable 3.1 mi (5 km) from the island, either with or without 
simultaneous drilling (Blackwell et al., 2004b).
    Other Operational Sounds: Open-water Season--Underwater and in-air 
production sounds from Northstar Island were recorded and characterized 
during nine open-water seasons from 2000 to 2008 (Blackwell and Greene, 
2006; Blackwell et al., 2009). Island activity sounds recorded during 
2000-2003 included construction of the island, installation of 
facilities, a large sealift transported by several barges and 
associated Ocean, River, and Point Class tugs, conversion of power 
generation from diesel-powered generators to Solar gas turbines, 
drilling, production, and reconstruction of an underwater berm for 
protection against ice. From 2003-2008 island activities mainly 
consisted of production related sounds and maintenance activities of 
the protection barrier. During the open water season, vessels were the 
main contributors to the underwater sound field at Northstar (Blackwell 
and Greene, 2006). Vessel noise is discussed in the next subsection.
    During both the construction phase in 2000 and the drilling and 
production phase, island sounds underwater reached background values at 
distances of 1.2-2.5 mi (2-4 km; Blackwell and Greene, 2006). For each 
year, percentile levels of broadband sound (maximum, 95th, 50th, and 
5th percentile, and minimum) were computed over the entire field 
season. The range of broadband levels recorded over 2001-2008 for all 
percentiles is 80.8-141 dB re 1 [micro]Pa. The maximum levels are 
mainly determined by the presence of vessels and can be governed by one 
specific event. The 95th percentile represents the sound level 
generated at Northstar during 95% of the time. From 2004 to 2008 these 
levels ranged from 110 to 119.5 dB re 1 [micro]Pa at approximately 0.3 
mi (450 m) from Northstar. Much of the variation in received levels was 
dependent on sea state, which is correlated with wind speed. The lowest 
sound levels in the time series are indicative of the quietest times in 
the water near the island and generally correspond to times with low 
wind speeds. Conversely, times of high wind speed usually correspond to 
increased broadband levels in the directional seafloor acoustic 
recorder (DASAR) record (Blackwell et al., 2009). The short-term 
variability in broadband sound levels in 2008 was higher than in 
previous years. This was attributed to the presence of a new type of 
impulsive sound on the records of the near-island DASARs, referred to 
as ``pops''. Bearings pointed to the northeastern part of Northstar 
Island, but to date the source is not known. Pops were broadband in 
nature, of short duration (approximately 0.05 s), and with received 
sound pressure levels at the near-island DASAR ranging from 107 to 144 
dB re 1 [mu]Pa. This sound was also present on the 2009 records, but 
the source remains unknown.
    Airborne sounds were recorded concurrently with the boat-based 
recordings in 2000-2003 (Blackwell and Greene, 2006). The strongest 
broadband airborne sounds were recorded approximately 985 ft (300 m) 
from Northstar Island in the presence of vessels, and reached 61-62 dBA 
re 20 [mu]Pa. These values are expressed as A-weighted levels on the 
scale normally used for in-air sounds. In-air sounds generally reached 
a minimum 0.6-2.5 mi (1-4 km) from the island, with or without the 
presence of boats.
(3) Transportation Sounds
    Sounds related to winter construction activities of Seal Island in 
1982 were reported by Greene (1983a) and information on this topic can 
be found in BP's 1999 application (BPXA, 1999). During the construction 
and operation of Northstar Island from 2000 to 2002, underwater sound 
from vehicles constructing and traveling along the ice road diminished 
to background levels at distances ranging from 2.9 to 5.9 mi (4.6 to 
9.5 km). In-air sound levels of these activities reached background 
levels at distances ranging from 328-1,969 ft (100-600 m; see Table 5 
in BP's application).
    Sounds and vibrations from vehicles traveling along an ice road 
constructed across the grounded sea ice and along Flaxman Island (a 
barrier Island east of Prudhoe Bay) were recorded in air and within 
artificially constructed polar bear dens in March 2002 (MacGillivray et 
al., 2003). Underwater recordings were not made. Sounds from vehicles 
traveling along the ice road were attenuated strongly by the snow cover 
of the artificial dens; broadband vehicle traffic noise was reduced by 
30-42 dB. Sound also diminished with increasing distance from the 
station. Most vehicle noise was indistinguishable from background 
(ambient) noise at 1,640 ft (500 m), although some vehicles were 
detectable to more than 1.2 mi (2,000 m). Ground vibrations (measured 
as velocity) were undetectable for most vehicles at a distance of 328 
ft (100 m) but were detectable to 656 ft (200 m) for a H[auml]gglunds 
tracked vehicle (MacGillivray et al., 2003).
    Helicopters were used for personnel and equipment transport to and 
from Northstar during the unstable ice periods in spring and fall. 
Helicopters flying to and from Northstar generally maintain straight-
line routes at altitudes of 1,000 ft (300 m) ASL, thereby limiting the 
received levels at and below the surface. Helicopter sounds contain 
numerous prominent tones at frequencies up to about 350 Hz, with the 
strongest measured tone at 20-22 Hz. Received peak sound levels of a 
Bell 212 passing over a hydrophone at an altitude of approximately 
1,000 ft (300 m), which is the minimum allowed altitude for the 
Northstar helicopter under normal operating conditions, varied between 
106 and 111 dB re 1 [mu]Pa at 30 and 59 ft (9 and 18 m) water depth 
(Greene, 1982, 1985). Harmonics of the main rotor and tail rotor 
usually dominate the sound from helicopters; however, many additional 
tones associated with the engines and other rotating parts are 
sometimes present (Patenaude et al., 2002).
    Under calm conditions, rotor and engine sounds are coupled into the 
water within a 26[deg] cone beneath the aircraft. Some of the sound 
transmits beyond the immediate area, and some sound enters the water 
outside the 26[deg] cone when the sea surface is rough. However, 
scattering and absorption limit lateral propagation in shallow water. 
For these reasons, helicopter and fixed-wing aircraft flyovers are not 
heard underwater for very long, especially when compared to how long 
they are heard in air as the aircraft approaches, passes and moves away

[[Page 39711]]

from an observer. Tones from helicopter traffic were detected 
underwater at a horizontal distance approximately 1,476 ft (450 m) from 
Northstar, but only during helicopter departures from Northstar 
(Blackwell et al., 2009). The duration of the detectable tones, when 
present, was short (20-50 s), and the received sound levels were weak, 
sometimes barely detectable. The lack of detectable tones during 65% of 
the investigated helicopter departures and arrivals supports the 
importance of the aircraft's path in determining whether tones will be 
detectable underwater. Helicopter tones were not detectable underwater 
at the most southern DASAR location approximately 4 mi (6.5 km) north 
of Northstar.
    Principally the crew boat, tugs, and self-propelled barges were the 
main contributors to the underwater sound field at Northstar during the 
construction and production periods (Blackwell and Greene, 2006). 
Vessel sounds are a concern due to the potential disturbance to marine 
mammals (Richardson et al., 1995b). Characteristics of underwater 
sounds from boats and vessels have been reported extensively, including 
specific measurements near Northstar (Greene and Moore, 1995; Blackwell 
and Greene, 2006). Broadband source levels for most small ships 
(lengths about 180-279 ft [55-85 m]) are approximately 160-180 dB re 1 
[mu]Pa. Both the crew boat and the tugs produced substantial broadband 
sound in the 50-2,000 Hz range, which could at least in part be 
accounted for by propeller cavitation (Ross, 1976). Several tones were 
also apparent in the vessel sounds, including one at 17.5 Hz, 
corresponding to the propeller blade rate of Ocean Class tugs. Two 
tones were identified for the crew boat: one at 52-55 Hz, which 
corresponds to the blade rate, and one at 22-26 Hz, which corresponds 
to a harmonic of the shaft rate.
    The presence of boats considerably expanded the distances to which 
Northstar-related sound was detectable. On days with average levels of 
background sounds, sounds from tug boats were detectable on offshore 
DASAR recordings to at least 13.4 mi (21.5 km) from Northstar 
(Blackwell et al., 2009). On other occasions, vessel sounds from crew 
boat, tugs, and self-propelled barges were often detectable underwater 
as much as approximately 18.6 mi (30 km) offshore (Blackwell and 
Greene, 2006). BP therefore looked into options to reduce vessel use. 
During the summer of 2003, a small, diesel-powered hovercraft (Griffon 
2000TD) was tested to transport crew and supplies between the mainland 
and Northstar Island. Acoustic measurements showed that the hovercraft 
was considerably quieter underwater than similar-sized conventional 
vessels (Blackwell and Greene, 2005). Received underwater broadband 
sound levels at 21.3 ft (6.5 m) from the hovercraft reached 133 and 131 
dB re 1 [mu]Pa for hydrophone depths 3 ft and 23 ft (1 m and 7 m), 
respectively. In-air unweighted and A-weighted broadband (10-10,000 Hz) 
levels reached 104 and 97 dB re 20 [mu]Pa, respectively. Use of the 
hovercraft for Northstar transport resulted in a decreased number of 
periods of elevated vessel noise in the acoustic records of the near-
island DASARs (Blackwell et al., 2009).

Description of Marine Mammals in the Area of the Specified Activity

    The Beaufort Sea supports a diverse assemblage of marine mammals, 
including: Bowhead, gray, beluga, killer, minke, and humpback whales; 
harbor porpoises; ringed, ribbon, spotted, and bearded seals; narwhals; 
polar bears; and walruses. The bowhead and humpback whales and polar 
bear are listed as ``endangered'' under the Endangered Species Act 
(ESA) and as depleted under the MMPA. Certain stocks or populations of 
gray, beluga, and killer whales and spotted seals are listed as 
endangered or are proposed for listing under the ESA; however, none of 
those stocks or populations occur in the proposed activity area. On 
December 10, 2010, NMFS published a notice of proposed threatened 
status for subspecies of the ringed seal (75 FR 77476) and a notice of 
proposed threatened and not warranted status for subspecies and 
distinct population segments of the bearded seal (75 FR 77496) in the 
Federal Register. Neither of these two ice seal species is considered 
depleted under the MMPA. Additionally, the ribbon seal is considered a 
``species of concern'' under the ESA. Both the walrus and the polar 
bear are managed by the U.S. Fish and Wildlife Service (USFWS) and are 
not considered further in this proposed rulemaking.
    Of the species mentioned here, the ones that are most likely to 
occur near the Northstar facility include: bowhead, gray, and beluga 
whales and ringed, bearded, and spotted seals. Ringed seals are year-
round residents in the Beaufort Sea and are anticipated to be the most 
frequently encountered species in the proposed project area. Bowhead 
whales are anticipated to be the most frequently encountered cetacean 
species in the proposed project area; however, their occurrence is not 
anticipated to be year-round. The most common time for bowheads to 
occur near Northstar is during the fall migration westward through the 
Beaufort Sea, which typically occurs from late August through October 
each year.
    Other marine mammal species that have been observed in the Beaufort 
Sea but are uncommon or rarely identified in the project area include 
harbor porpoise, narwhal, killer, minke, and humpback whales, and 
ribbon seals. These species could occur in the project area, but each 
of these species is uncommon or rare in the area and relatively few 
encounters with these species are expected during BP's activities. The 
narwhal occurs in Canadian waters and occasionally in the Beaufort Sea, 
but it is rare there and is not expected to be encountered. There are 
scattered records of narwhal in Alaskan waters, including reports by 
subsistence hunters, where the species is considered extralimital 
(Reeves et al., 2002). Point Barrow, Alaska, is the approximate 
northeastern extent of the harbor porpoise's regular range (Suydam and 
George, 1992), though there are extralimital records east to the mouth 
of the Mackenzie River in the Northwest Territories, Canada, and recent 
sightings in the Beaufort Sea in the vicinity of Prudhoe Bay during 
surveys in 2007 and 2008 (Christie et al., 2009). Monnett and Treacy 
(2005) did not report any harbor porpoise sightings during aerial 
surveys in the Beaufort Sea from 2002 through 2004. Humpback and minke 
whales have recently been sighted in the Chukchi Sea but very rarely in 
the Beaufort Sea. Greene et al. (2007) reported and photographed a 
humpback whale cow/calf pair east of Barrow near Smith Bay in 2007, 
which is the first known occurrence of humpbacks in the Beaufort Sea. 
Savarese et al. (2009) reported one minke whale sighting in the 
Beaufort Sea in 2007 and 2008. Ribbon seals do not normally occur in 
the Beaufort Sea; however, two ribbon seal sightings were reported 
during vessel-based activities near Prudhoe Bay in 2008 (Savarese et 
al., 2009). Due to the rarity of these species in the proposed project 
area and the remote chance they would be affected by BP's proposed 
activities at Northstar, these species are not discussed further in 
these proposed regulations.
    BP's application contains information on the status, distribution, 
seasonal distribution, and abundance of each of the six species under 
NMFS jurisdiction likely to be impacted by the proposed activities. 
When reviewing the application, NMFS determined that the species 
descriptions provided by BP correctly characterized the status,

[[Page 39712]]

distribution, seasonal distribution, and abundance of each species. 
Please refer to the application for that information (see ADDRESSES). 
Additional information can also be found in the NMFS Stock Assessment 
Reports (SAR). The 2010 Alaska Marine Mammal SAR is available on the 
Internet at: https://www.nmfs.noaa.gov/pr/pdfs/sars/ak2010.pdf.

Brief Background on Marine Mammal Hearing

    When considering the influence of various kinds of sound on the 
marine environment, it is necessary to understand that different kinds 
of marine life are sensitive to different frequencies of sound. Based 
on available behavioral data, audiograms have been derived using 
auditory evoked potentials, anatomical modeling, and other data, 
Southall et al. (2007) designate ``functional hearing groups'' for 
marine mammals and estimate the lower and upper frequencies of 
functional hearing of the groups. The functional groups and the 
associated frequencies are indicated below (though animals are less 
sensitive to sounds at the outer edge of their functional range and 
most sensitive to sounds of frequencies within a smaller range 
somewhere in the middle of their functional hearing range):
     Low frequency cetaceans (13 species of mysticetes): 
functional hearing is estimated to occur between approximately 7 Hz and 
22 kHz (however, a study by Au et al. (2006) of humpback whale songs 
indicate that the range may extend to at least 24 kHz);
     Mid-frequency cetaceans (32 species of dolphins, six 
species of larger toothed whales, and 19 species of beaked and 
bottlenose whales): functional hearing is estimated to occur between 
approximately 150 Hz and 160 kHz;
     High frequency cetaceans (eight species of true porpoises, 
six species of river dolphins, Kogia, the franciscana, and four species 
of cephalorhynchids): functional hearing is estimated to occur between 
approximately 200 Hz and 180 kHz;
     Pinnipeds in Water: functional hearing is estimated to 
occur between approximately 75 Hz and 75 kHz, with the greatest 
sensitivity between approximately 700 Hz and 20 kHz; and
     Pinnipeds in Air: functional hearing is estimated to occur 
between approximately 75 Hz and 30 kHz.
    As mentioned previously in this document, six marine mammal species 
(three cetacean and three pinniped species) are likely to occur in the 
Northstar facility area. Of the three cetacean species likely to occur 
in BP's project area, two are classified as low frequency cetaceans 
(i.e., bowhead and gray whales) and one is classified as a mid-
frequency cetacean (i.e., beluga whales) (Southall et al., 2007).
    Underwater audiograms have been obtained using behavioral methods 
for four species of phocinid seals: the ringed, harbor, harp, and 
northern elephant seals (reviewed in Richardson et al., 1995b; Kastak 
and Schusterman, 1998). Below 30-50 kHz, the hearing threshold of 
phocinids is essentially flat down to at least 1 kHz and ranges between 
60 and 85 dB re 1 [mu]Pa. There are few published data on in-water 
hearing sensitivity of phocid seals below 1 kHz. However, measurements 
for one harbor seal indicated that, below 1 kHz, its thresholds 
deteriorated gradually to 96 dB re 1 [mu]Pa at 100 Hz from 80 dB re 1 
[mu]Pa at 800 Hz and from 67 dB re 1 [mu]Pa at 1,600 Hz (Kastak and 
Schusterman, 1998). More recent data suggest that harbor seal hearing 
at low frequencies may be more sensitive than that and that earlier 
data were confounded by excessive background noise (Kastelein et al., 
2009a,b). If so, harbor seals have considerably better underwater 
hearing sensitivity at low frequencies than do small odontocetes like 
belugas (for which the threshold at 100 Hz is about 125 dB). In air, 
the upper frequency limit of phocid seals is lower (about 20 kHz).
    Pinniped call characteristics are relevant when assessing potential 
masking effects of man-made sounds. In addition, for those species 
whose hearing has not been tested, call characteristics are useful in 
assessing the frequency range within which hearing is likely to be most 
sensitive. The three species of seals present in the study area, all of 
which are in the phocid seal group, are all most vocal during the 
spring mating season and much less so during late summer. In each 
species, the calls are at frequencies from several hundred to several 
thousand hertz--above the frequency range of the dominant noise 
components from most of the proposed oil production and operational 
activities.
    Cetacean hearing has been studied in relatively few species and 
individuals. The auditory sensitivity of bowhead, gray, and other 
baleen whales has not been measured, but relevant anatomical and 
behavioral evidence is available. These whales appear to be specialized 
for low frequency hearing, with some directional hearing ability 
(reviewed in Richardson et al., 1995b; Ketten, 2000). Their optimum 
hearing overlaps broadly with the low frequency range where BP's 
production activities and associated vessel traffic emit most of their 
energy.
    The beluga whale is one of the better-studied species in terms of 
its hearing ability. As mentioned earlier, the auditory bandwidth in 
mid-frequency odontocetes is believed to range from 150 Hz to 160 kHz 
(Southall et al., 2007); however, belugas are most sensitive above 10 
kHz. They have relatively poor sensitivity at the low frequencies 
(reviewed in Richardson et al., 1995b) that dominate the sound from 
industrial activities and associated vessels. Nonetheless, the noise 
from strong low frequency sources is detectable by belugas many 
kilometers away (Richardson and Wursig, 1997). Also, beluga hearing at 
low frequencies in open-water conditions is apparently somewhat better 
than in the captive situations where most hearing studies were 
conducted (Ridgway and Carder, 1995; Au, 1997). If so, low frequency 
sounds emanating from production activities may be detectable somewhat 
farther away than previously estimated.
    Call characteristics of cetaceans provide some limited information 
on their hearing abilities, although the auditory range often extends 
beyond the range of frequencies contained in the calls. Also, 
understanding the frequencies at which different marine mammal species 
communicate is relevant for the assessment of potential impacts from 
manmade sounds. A summary of the call characteristics for bowhead, 
gray, and beluga whales is provided next. More information is available 
in BP's application (see ADDRESSES).
    Most bowhead calls are tonal, frequency-modulated sounds at 
frequencies of 50-400 Hz. These calls overlap broadly in frequency with 
the underwater sounds emitted by many construction and operational 
activities (Richardson et al., 1995b). Source levels are quite 
variable, with the stronger calls having source levels up to about 180 
dB re 1 [micro]Pa at 1 m. Gray whales make a wide variety of calls at 
frequencies from < 100-2,000 Hz (Moore and Ljungblad, 1984; Dalheim, 
1987).
    Beluga calls include trills, whistles, clicks, bangs, chirps and 
other sounds (Schevill and Lawrence, 1949; Ouellet, 1979; Sjare and 
Smith, 1986a). Beluga whistles have dominant frequencies in the 2-6 kHz 
range (Sjare and Smith, 1986a). This is above the frequency range of 
most of the sound energy produced by the planned Northstar production 
activities and associated vessels. Other beluga call types reported by 
Sjare and Smith (1986a,b) included

[[Page 39713]]

sounds at mean frequencies ranging upward from 1 kHz.
    The beluga also has a very well developed high frequency 
echolocation system, as reviewed by Au (1993). Echolocation signals 
have peak frequencies from 40-120 kHz and broadband source levels of up 
to 219 dB re 1 [mu]Pa-m (zero-peak). Echolocation calls are far above 
the frequency range of the sounds from the planned Northstar 
activities. Therefore, those industrial sounds are not expected to 
interfere with echolocation.

Potential Effects of the Specified Activity on Marine Mammals

    The likely or possible impacts of the planned offshore oil 
developments at Northstar 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. In winter, during ice road construction, and in spring, 
flooding on the sea ice may displace some ringed seals along the ice 
road corridor. There is a small chance that a seal pup might be injured 
or killed by on-ice construction or transportation activities. A major 
oil spill is unlikely and, if it occurred, its effects are difficult to 
predict. Potential impacts from an oil spill are discussed in more 
detail later in this section.
    Petroleum development and associated activities in marine waters 
introduce sound into the environment, produced by island construction, 
maintenance, and drilling, as well as vehicles operating on the ice, 
vessels, aircraft, generators, production machinery, gas flaring, and 
camp operations. The potential effects of sound from the proposed 
activities might include one or more of the following: masking of 
natural sounds; behavioral disturbance and associated habituation 
effects; and, at least in theory, temporary or permanent hearing 
impairment. As outlined in previous NMFS documents, the effects of 
noise on marine mammals are highly variable, and can be categorized as 
follows (based on Richardson et al., 1995b):
    (1) The noise may be too weak to be heard at the location of the 
animal (i.e., lower than the prevailing ambient noise level, the 
hearing threshold of the animal at relevant frequencies, or both);
    (2) The noise may be audible but not strong enough to elicit any 
overt behavioral response;
    (3) The noise may elicit reactions of variable conspicuousness and 
variable relevance to the well being of the marine mammal; these can 
range from temporary alert responses to active avoidance reactions such 
as vacating an area at least until the noise event ceases but 
potentially for longer periods of time;
    (4) Upon repeated exposure, a marine mammal may exhibit diminishing 
responsiveness (habituation), or disturbance effects may persist; the 
latter is most likely with sounds that are highly variable in 
characteristics, infrequent, and unpredictable in occurrence, and 
associated with situations that a marine mammal perceives as a threat;
    (5) Any anthropogenic noise that is strong enough to be heard has 
the potential to reduce (mask) the ability of a marine mammal to hear 
natural sounds at similar frequencies, including calls from 
conspecifics, and underwater environmental sounds such as surf noise;
    (6) If mammals remain in an area because it is important for 
feeding, breeding, or some other biologically important purpose even 
though there is chronic exposure to noise, it is possible that there 
could be noise-induced physiological stress; this might in turn have 
negative effects on the well-being or reproduction of the animals 
involved; and
    (7) Very strong sounds have the potential to cause a temporary or 
permanent reduction in hearing sensitivity. In terrestrial mammals, and 
presumably marine mammals, received sound levels must far exceed the 
animal's hearing threshold for there to be any temporary threshold 
shift (TTS) in its hearing ability. For transient sounds, the sound 
level necessary to cause TTS is inversely related to the duration of 
the sound. Received sound levels must be even higher for there to be 
risk of permanent hearing impairment. In addition, intense acoustic or 
explosive events may cause trauma to tissues associated with organs 
vital for hearing, sound production, respiration and other functions. 
This trauma may include minor to severe hemorrhage.
    The characteristics of the various sound sources at Northstar were 
summarized earlier in this document (see the ``Description of the 
Specified Activity'' section). Additionally, BP's application contains 
more details on the Northstar sound characteristics, underwater and in-
air sound propagation in and around Northstar, and ambient noise levels 
in the waters near Prudhoe Bay, Alaska. Please refer to that document 
for more information (see ADDRESSES).

Potential Effects of Sound on Cetaceans

(1) Masking
    Masking is the obscuring of sounds of interest by other sounds, 
often at similar frequencies. Marine mammals are highly dependent on 
sound, and their ability to recognize sound signals amid other noise is 
important in communication, predator and prey detection, and, in the 
case of toothed whales, echolocation. Even in the absence of manmade 
sounds, the sea is usually noisy. Background ambient noise often 
interferes with or masks the ability of an animal to detect a sound 
signal even when that signal is above its absolute hearing threshold. 
Natural ambient noise includes contributions from wind, waves, 
precipitation, other animals, and (at frequencies above 30 kHz) thermal 
noise resulting from molecular agitation (Richardson et al., 1995b). 
Background noise also can include sounds from human activities. Masking 
of natural sounds can result when human activities produce high levels 
of background noise. Conversely, if the background level of underwater 
noise is high (e.g., on a day with strong wind and high waves), an 
anthropogenic noise source will not be detectable as far away as would 
be possible under quieter conditions and will itself be masked.
    Although some degree of masking is inevitable when high levels of 
manmade broadband sounds are introduced into the sea, marine mammals 
have evolved systems and behavior that function to reduce the impacts 
of masking. Structured signals, such as the echolocation click 
sequences of small toothed whales, may be readily detected even in the 
presence of strong background noise because their frequency content and 
temporal features usually differ strongly from those of the background 
noise (Au and Moore, 1988, 1990). The components of background noise 
that are similar in frequency to the sound signal in question primarily 
determine the degree of masking of that signal.
    Redundancy and context can also facilitate detection of weak 
signals. These phenomena may help marine mammals detect weak sounds in 
the presence of natural or manmade noise. Most masking studies in 
marine mammals present the test signal and the masking noise from the 
same direction. The sound localization abilities of marine mammals 
suggest that, if signal and noise come from different directions, 
masking would not be as severe as the usual types of masking studies 
might suggest (Richardson et al., 1995b). The dominant background noise

[[Page 39714]]

may be highly directional if it comes from a particular anthropogenic 
source such as a ship or industrial site. Directional hearing may 
significantly reduce the masking effects of these noises by improving 
the effective signal-to-noise ratio. In the cases of high-frequency 
hearing by the bottlenose dolphin, beluga whale, and killer whale, 
empirical evidence confirms that masking depends strongly on the 
relative directions of arrival of sound signals and the masking noise 
(Penner et al., 1986; Dubrovskiy, 1990; Bain et al., 1993; Bain and 
Dahlheim, 1994). Toothed whales, and probably other marine mammals as 
well, have additional capabilities besides directional hearing that can 
facilitate detection of sounds in the presence of background noise. 
There is evidence that some toothed whales can shift the dominant 
frequencies of their echolocation signals from a frequency range with a 
lot of ambient noise toward frequencies with less noise (Au et al., 
1974, 1985; Moore and Pawloski, 1990; Thomas and Turl, 1990; Romanenko 
and Kitain, 1992; Lesage et al., 1999). A few marine mammal species are 
known to increase the source levels or alter the frequency of their 
calls in the presence of elevated sound levels (Dahlheim, 1987; Au, 
1993; Lesage et al., 1993, 1999; Terhune, 1999; Foote et al., 2004; 
Parks et al., 2007, 2009; Di Iorio and Clark, 2009; Holt et al., 2009).
    These data demonstrating adaptations for reduced masking pertain 
mainly to the very high frequency echolocation signals of toothed 
whales. There is less information about the existence of corresponding 
mechanisms at moderate or low frequencies or in other types of marine 
mammals. For example, Zaitseva et al. (1980) found that, for the 
bottlenose dolphin, the angular separation between a sound source and a 
masking noise source had little effect on the degree of masking when 
the sound frequency was 18 kHz, in contrast to the pronounced effect at 
higher frequencies. Directional hearing has been demonstrated at 
frequencies as low as 0.5-2 kHz in several marine mammals, including 
killer whales (Richardson et al., 1995b). This ability may be useful in 
reducing masking at these frequencies. In summary, high levels of noise 
generated by anthropogenic activities may act to mask the detection of 
weaker biologically important sounds by some marine mammals. This 
masking may be more prominent for lower frequencies. For higher 
frequencies, such as that used in echolocation by toothed whales, 
several mechanisms are available that may allow them to reduce the 
effects of such masking.
    There would be no masking effects on cetaceans from BP's proposed 
activities during the ice-covered season because cetaceans will not 
occur near Northstar at that time. The sounds from oil production and 
any drilling activities are not expected to be detectable beyond 
several kilometers from the source (Greene, 1983; Blackwell et al., 
2004b; Blackwell and Greene, 2005, 2006). Sounds from vessel activity, 
however, were detectable to distances as far as approximately 18.6 mi 
(30 km) from Northstar (Blackwell and Greene, 2006). Vessels under 
power to maintain position can be a source of continuous noise in the 
marine environment (Blackwell et al., 2004b; Blackwell and Greene, 
2006) and therefore have the potential to cause some degree of masking.
    Small numbers of bowheads, belugas and (rarely) gray whales could 
be present near Northstar during the open-water season. Almost all 
energy in the sounds emitted by drilling and other operational 
activities is at low frequencies, predominantly below 250 Hz with 
another peak centered around 1,000 Hz. Most energy in the sounds from 
the vessels and aircraft to be used during this project is below 1 kHz 
(Moore et al., 1984; Greene and Moore, 1995; Blackwell et al., 2004b; 
Blackwell and Greene, 2006). These frequencies are mainly used by 
mysticetes but not by odontocetes. Therefore, masking effects would 
potentially be more pronounced in the bowhead and gray whales that 
might occur in the proposed project area.
    Because of the relatively low effective source levels and rapid 
attenuation of drilling and production sounds from artificial islands 
in shallow water, masking effects are unlikely even for mysticetes that 
are within several kilometers of Northstar Island. Vessels that are 
docking or under power to maintain position could cause some degree of 
masking. However, the adaptation of some cetaceans to alter the source 
level or f