Small Takes of Marine Mammals Incidental to Specified Activities; Seismic Surveys in the Beaufort and Chukchi Seas off Alaska, 32045-32059 [06-5025]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 71, Number 106 (Friday, June 2, 2006)]
[Notices]
[Pages 32045-32059]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 06-5025]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[I.D. 032906E]


Small Takes of Marine Mammals Incidental to Specified Activities; 
Seismic Surveys in the Beaufort and Chukchi Seas off Alaska

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

ACTION:  Notice of receipt of application and proposed incidental take 
authorization; request for comments.

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SUMMARY:  NMFS has received an application from GX Technologies, Inc of 
Houston, TX (GXT) for an Incidental Harassment Authorization (IHA) to 
take small numbers of marine mammals, by harassment, incidental to 
conducting a marine geophysical program, including deep seismic 
surveys, on oil and gas lease blocks located on Outer Continental Shelf 
(OCS) waters in the Chukchi Sea. Under the Marine Mammal Protection Act 
(MMPA), NMFS

[[Page 32046]]

is requesting comments on its proposal to issue an IHA to GXT to 
incidentally take, by harassment, small numbers of several species of 
marine mammals between June and November, 2006 incidental to conducting 
seismic surveys.

DATES:  Comments and information must be received no later than July 3, 
2006.

ADDRESSES:  Comments on the application should be addressed to P. 
Michael Payne, Chief, Permits, Conservation and Education Division, 
Office of Protected Resources, National Marine Fisheries Service, 1315 
East-West Highway, Silver Spring, MD 20910-3225, or by telephoning one 
of the contacts listed here. The mailbox address for providing email 
comments is PR1.032906E @noaa.gov. Comments sent via e-mail, including 
all attachments, must not exceed a 10-megabyte file size. A copy of the 
application (containing a list of the references used in this document) 
may be obtained by writing to this address or by telephoning the 
contact listed here and is also available at: https://www.nmfs.noaa.gov/
pr/permits/incidental.htmsign;iha.
    A copy of Minerals Management Service's (MMS) Programmatic 
Environmental Assessment (PEA) is available on-line at: https://
www.mms.gov/alaska/ref/eis_ea.htm.
    Documents cited in this document, that are not available through 
standard public library access may be viewed, by appointment, during 
regular business hours at this address.

FOR FURTHER INFORMATION CONTACT:  Kenneth Hollingshead or Jolie 
Harrison, Office of Protected Resources, NMFS, (301) 713-2289.

SUPPLEMENTARY INFORMATION:

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct 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 if certain 
findings are made and either regulations are issued or, if the taking 
is limited to harassment, a notice of a proposed authorization is 
provided to the public for review.
    An authorization 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 subsistence uses and that the permissible methods of 
taking and requirements pertaining to the mitigation, monitoring and 
reporting of such takings 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.''
    Section 101(a)(5)(D) of the MMPA established an expedited process 
by which citizens of the United States can apply for an authorization 
to incidentally take small numbers of marine mammals by harassment. 
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].
    Section 101(a)(5)(D) establishes a 45-day time limit for NMFS 
review of an application followed by a 30-day public notice and comment 
period on any proposed authorizations for the incidental harassment of 
marine mammals. Within 45 days of the close of the comment period, NMFS 
must either issue or deny issuance of the authorization.

Summary of Request

    On March 28, 2006, NMFS received an IHA application from GXT to 
take several species of marine mammals incidental to conducting a 
marine seismic survey in the Chukchi and Beaufort Seas. On March 31, 
2006, GXT notified NMFS that it would not be conducting surveys in the 
U.S. Beaufort Sea, but would instead conduct seismic surveys in the 
Canadian Beaufort Sea.
    GXT plans to collect seismic reflection data that reveal the sub-
bottom profile for assessments of petroleum reserves in the area. 
Ultra-deep 2D lines such as those to be collected are used to better 
evaluate the evolution of the petroleum system at the basin level, 
including identifying source rocks, migration pathways, and play types. 
All planned geophysical data acquisition activities will be conducted 
by GXT. The geophysical survey will be performed from the M/V 
Discoverer II.
    The M/V Discoverer II will arrive in Dutch Harbor about June 1st 
where it will be resupplied and the crew will change in preparation for 
the beginning of seismic surveys in the Chukchi Sea. Depending on ice 
conditions, the vessel will mobilize to arrive off Cape Lisburne and 
begin survey data acquisition as soon as possible; the expected date is 
June 15, 2006, depending upon ice conditions. Two alternative schedule 
scenarios are planned depending on the seasonal ice conditions 
encountered in 2006.
    The primary (and most likely) scenario entails operations beginning 
in the Chukchi Sea about July 10, 2006. Collection of seismic data will 
continue there until about July 25th or whenever there is sufficient 
open water near Point Barrow and in the Alaskan Beaufort Sea to allow 
passage east into the Canadian Beaufort Sea. The M/V Discoverer II will 
then proceed out of the Chukchi Sea, traverse the Alaskan Beaufort Sea, 
and begin surveying within the Canadian Beaufort Sea. Seismic 
operations will continue in the Canadian Beaufort Sea until all planned 
seismic lines have been completed, or new ice begins forming in the 
fall. The vessel will then travel west across the Beaufort Sea and 
return to the Chukchi Sea to complete any lines not surveyed in July, 
or until weather and sea ice force an end to the survey season, which 
is not expected to continue past November 30, 2006.
    The second scenario will occur only if sea ice in the Beaufort Sea 
does not move far enough offshore to allow the M/V Discoverer II to 
travel to the Canadian Beaufort. In that case, the vessel will continue 
operations in the Chukchi Sea until all survey lines there are 
completed. The M/V Discoverer II will then exit the area and transit to 
Dutch Harbor to de-mobilize. Helicopter operations are not planned as a 
part of the seismic survey and would occur only in the case of an 
emergency.
    The total seismic survey program, if it can be completed, will 
consist of a total of about 5302 km (3294.5 mi) of surveys, not 
including transits when the airguns are not operating. Water depths 
within the study area are 30-3800 m (98-12467 ft). Approximately 14 
percent of the survey (about 742 km (461 mi)) will occur in water 
depths greater than 500 m (1640 ft), 5 percent of the survey (about 265 
km (165 mi)) will be conducted in water 200-500 m (656-1640 ft) deep, 
and most (81 percent) of the survey (about 4295 km (2669 mi)) will 
occur in water less than 200 m (656 ft). None of the survey will take 
place in nearshore waters within 25 km (15.5 mi) of the coast (the 
Chukchi polynya zone).
    The M/V Discoverer II will tow an airgun array directly astern and 
a single hydrophone streamer up to 9 km long. The array will consist of 
36 sleeve airguns (eight 40 in\3\, four 70 in\3\, four

[[Page 32047]]

80 in\3\, tweleve 100 in\3\, and eight 150 in\3\) that produce a total 
discharge of 3320 in\3\. The vessel will travel along pre-determined 
lines at about 4-5 knots while the airgun array discharges about every 
20 seconds (shot interval about 46 m (151 ft). The towed hydrophone 
streamer will receive the reflected signals and transfer the data to an 
on-board processing system. The proposed survey lines cover a large 
portion of the Chukchi Sea, and tie together known wells, core 
locations, fault lines and other geophysical points of interest. 
Specifications of the M/V Discoverer II and the 36-airgun array that 
will be used can be found in GXT's application (Appendices A and B).
    The survey consists of a large grid of 14 lines oriented to connect 
previous well locations and core sample locations as well as geological 
structures in the sub-surface. The extent of the lines allows 
flexibility to mitigate any interaction with seasonal subsistence 
hunting as well as species migration patterns. GXT has restricted its 
survey lines along the shore to the area of the MMS lease sales 
(greater than 25 km (15.5 mi) offshore) to exclude the nearshore 
Chukchi polynya, through which marine mammals migrate in the spring. 
Lines will be chosen based on marine mammal migration and subsistence 
hunting, as well as ice movement and geophysical importance. If heavy 
ice conditions are encountered in the northern portions of the survey 
area, some trackline planned for that region may be shifted to ice-free 
waters within the central or southern portions of the survey area. 
There will be additional seismic operations associated with airgun 
testing, start up, and repeat coverage of any areas where initial data 
quality is sub-standard. In addition to the airgun array, a pinger 
system will be used to position the 36-airgun array and streamer 
relative to the vessel.
    The M/V Discoverer II will serve as the platform from which vessel-
based marine mammal observers will watch for marine mammals before and 
during airgun operations (see Mitigation and Monitoring later in this 
document). A ``chase boat'' will be used to protect the streamer from 
damage and otherwise lend support to the M/V Discoverer II. It will not 
be introducing sounds into the water beyond those associated with 
normal vessel operations.

Characteristics of Airgun Pulses

    Discussion of the characteristics of airgun pulses was provided in 
several previous Federal Register documents (see 69 FR 31792 (June 7, 
2004) or 69 FR 34996 (June 23, 2004)) and is not repeated here. 
Additional information can be found in the MMS PEA and Appendix C in 
GXT's application. Reviewers are encouraged to read these documents for 
additional information.

Safety Radii

    The rms (root mean square) received sound pressure levels that are 
used as impact criteria for marine mammals in U.S. marine mammal 
research are not directly comparable to the peak or peak-to-peak values 
normally used by geophysicists to characterize source levels of airguns 
(GXT IHA Application, Appendix C). The measurement units used to 
describe airgun sources, peak or peak-to-peak dB, are always higher 
than the rms dB referred to in much of the biological literature and by 
NMFS. A measured broadband received level of 160 dB re 1 microPa (rms) 
in the far field would typically correspond to a peak measurement of 
about 170 to 172 dB, and to a peak-to-peak measurement of about 176 to 
178 decibels, as measured for the same pulse received at the same 
location (Greene, 1997; McCauley et al.,1998, 2000a). The precise 
difference between rms and peak or peak-to-peak values for a given 
pulse depends on the frequency content and duration of the pulse, among 
other factors. However, the rms level is always lower than the peak or 
peak-to-peak level for an airgun-type source.
    Received sound fields have been modeled by GXT using the Gundalf 
software suite (Gundalf, 2002) for the 36-airgun array that will be 
used during this survey (GXT IHA Application Appendix B). GXT used an 
advanced version of the Gundalf modeling program to estimate the rms 
received sound levels (in dB re 1 microPa) at different distances from 
the seismic source on a broadband basis (0-256 Hz). These estimates are 
believed by GXT to be conservative (i.e., likely to overestimate the 
distance at which received levels will be [gteqt]160 dB) and most 
applicable to the 36-airgun array discharging 3320 in\3\ in water 
depths between 200 and 500 m (656-1640 ft), or ``intermediate depths.'' 
The safety radii are expected by GXT to be smaller in ``deep'' (greater 
than 500 m) and ``shallow'' (less than 200 m) water. Empirical data do 
not exist for this airgun array's sound propagation, so those data will 
be collected at the beginning of seismic operations. During this 
initial period, a 1.5X precautionary factor will be applied to the 190 
dB and 180 dB radii listed here in Table 1, for use as shutdown radii 
for marine mammals in the water. Once empirical measurements of the 
sound produced by GXT's airgun array have been collected, the safety 
radii presented in Table 1 may be adjusted to reflect those results.
    For purposes of estimating sound exposures in this document, the 
intermediate depth radii (expected by GXT to be the largest of the 
radii for any of the three water depth categories) will be used along 
tracklines occurring in all three depth categories. GXT believes this 
precautionary procedure will likely overestimate the area ensonified 
and, therefore, the numbers of marine mammals exposed to various 
applicable received sound levels.
    As discussed in detail later in this document (see Mitigation), the 
airguns will be powered down immediately (or shut down if necessary) 
when marine mammals are detected within or about to enter the 
appropriate [gteqt]180 dB or [gteqt]190 dB radii. A single 40 in\3\ 
sleeve airgun will be used as the power down source. The 160-190 dB re 
1 microPa (rms) radii for this source will be measured during acoustic 
verification measurements at the beginning of seismic shooting.

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[GRAPHIC] [TIFF OMITTED] TN02JN06.013

Description of Habitat and Marine Mammals Affected by the Activity

    A detailed description of the Chukchi Sea ecosystem and its 
associated marine mammals can be found in several documents, including 
the MMS PEA and does not need to be repeated here.

Marine Mammals

    The Chukchi Seas support a diverse assemblage of marine mammals, 
including bowhead whales (Balaena mysticetus), gray whales 
(Eschrichtius robustus), beluga whales (Delphinapterus leucas), killer 
whales (Orcinus orca), harbor porpoise (Phocoena phocoena), ringed 
seals (Phoca hispida), spotted seals (Phoca largha), bearded seals 
(Erignathus barbatus), walrus (Odobenus rosmarus) and polar bears 
(Ursus maritimus). These latter two species are under the jurisdiction 
of the U.S. Fish and Wildlife Service (USFWS) and are not discussed 
further in this document. Abundance estimates of these species can be 
found in Table 2 in GXT's application. Descriptions of the biology and 
distribution of the marine mammal species under NMFS' jurisdiction can 
be found in GXT's application, MMS' PEA, and several other documents 
(Corps of Engineers, 1999; Lentfer, 1988; MMS, 1992, 1996; Hill et al., 
1999). Information on marine mammal hearing capabilities can be found 
in GXT's application.
    Information on these species can also be found in NMFS Stock 
Assessment Reports. The Alaska stock assessment document is available 
at: https://www.nmfs.noaa.gov/pr/readingrm/MMSARS/sar2003akfinal.pdf. 
Updated species reports are available at: https://www.nmfs.noaa.gov/pr/
readingrm/MMSARS/2005alaskasummarySARs.pdf. Please refer to these 
documents for information on these species.

Potential Impacts of Seismic Surveys on Marine Mammals

    Disturbance by seismic noise is the principal means of taking by 
this activity. Support vessels and marine mammal survey aircraft (if 
required) may provide a potential secondary source of noise. The 
physical presence of vessels and aircraft could also lead to non-
acoustic effects on marine mammals involving visual or other cues.
    As outlined in several previous NMFS documents, the effects of 
noise on marine mammals are highly variable, and can be categorized as 
follows (based on Richardson et al., 1995):
    (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;
    (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;

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    (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 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.

Potential Effects of Seismic Airgun Arrays on Marine Mammals

    GXT believes that the effects of sounds from airguns might include 
one or more of the following: (1) Tolerance; (2) masking of natural 
sounds; (2) behavioral disturbance; and (3) at least in theory, hearing 
impairment and other non-auditory physical effects (Richardson et al., 
1995). Discussion on marine mammal tolerance to noise, masking effects 
of noise, temporary or permanent hearing impairment, and non-auditory 
effects can be found in GXT's IHA application and previous IHAs for 
seismic activities (e.g., see 69 FR 74906, December 14, 2004). In 
summary, GXT believes that it is unlikely that there would be any cases 
of temporary or permanent hearing impairment, non-auditory physical 
effects or strandings. However, because of public interest in potential 
behavioral disturbance and marine mammal strandings by seismic arrays, 
NMFS has provided GXT's analysis of those topics in this document.
    NMFS has also provided information previously on the potential 
effects of noise on marine mammal species expected to be in the Chukchi 
Sea region (see 71 FR 26055, May 3, 2006). Readers are encouraged to 
review those documents for additional information.
Behavioral Disturbance
    Disturbance to marine mammals includes a variety of effects, 
including subtle changes in behavior, more conspicuous changes in 
activities, and displacement. Reactions to sound, if any, depend on 
species, state of maturity, experience, current activity, reproductive 
state, time of day, and many other factors. Given the many 
uncertainties in predicting the quantity and types of impacts of noise 
on marine mammals, it is common practice to estimate how many mammals 
will be present within a particular distance of industrial activities, 
or exposed to a particular level of industrial sound. The sound 
criteria used to estimate how many marine mammals might be disturbed to 
some biologically-important degree by a seismic program are based on 
behavioral observations during studies of several species. However, 
information is lacking for many species. Detailed studies have been 
done on humpback, gray, and bowhead whales, and on ringed seals. Less 
detailed data are available for some other species of baleen whales, 
sperm whales, and small whales.
Baleen Whales
    According to GXT, baleen whales generally tend to avoid operating 
airguns, but avoidance radii are quite variable. Whales are often 
reported to show no overt reactions to pulses from large arrays of 
airguns at distances beyond a few kilometers, even though the airgun 
pulses remain well above ambient noise levels out to much longer 
distances. However, baleen whales exposed to strong noise pulses from 
airguns often react by deviating from their normal migration route and/
or interrupting their feeding and moving away (see GXT's IHA 
Application Appendix C for detailed information). In the case of 
migrating gray and bowhead whales, the observed changes in behavior 
appeared to be of little or no biological consequence to the animals. 
They simply avoided the sound source by displacing their migration 
route to varying degrees, but within the natural boundaries of the 
migration corridors.
    Studies of gray, bowhead, and humpback whales have determined that 
received levels of pulses in the 160-170 dB re 1 microPa rms range seem 
to cause obvious avoidance behavior in a substantial fraction of the 
animals exposed. In many areas, seismic pulses from large arrays of 
airguns diminish to those sound levels at distances ranging from 4.5 to 
14.5 km (2.8 to 9 mi) from the source. A substantial proportion of the 
baleen whales within those distances may show avoidance or other strong 
disturbance reactions to the airgun array. Subtle behavioral changes 
sometimes become evident at somewhat lower received levels, and recent 
studies (see Appendix C) show that some species of baleen whales, 
notably bowhead and humpback whales, at times show strong avoidance at 
received levels lower than 160-170 dB re 1 microPa rms. Bowhead whales 
migrating west across the Alaskan Beaufort Sea in autumn, in 
particular, are unusually responsive, with substantial avoidance 
occurring out to distances of 20-30 km (12.4-18.6 mi) from a medium-
sized airgun source (Miller et al., 1999; Richardson et al., 1999; see 
Appendix C). More recent research on bowhead whales (Miller et al., 
2005) corroborates earlier evidence that, during the summer feeding 
season, bowheads are not as sensitive to seismic sources. In summer, 
bowheads typically begin to show avoidance reactions at a received 
level of about 160-170 dB re 1 microPa rms (Richardson et al., 1986; 
Ljungblad et al., 1988; Miller et al., 1999). The GXT project is to be 
partly in summer, when feeding bowheads might be encountered (although 
the primary bowhead summer feeding grounds are far to the east in the 
Canadian Beaufort Sea), and partly in autumn, when the bowheads are 
commonly involved in migration (though bowheads also continue to feed 
in autumn).
    Malme et al. (1986, 1988) studied the responses of feeding eastern 
gray whales to pulses from a single 100 in\3\ airgun off St. Lawrence 
Island in the northern Bering Sea. They estimated, based on small 
sample sizes, that 50 percent of feeding gray whales ceased feeding at 
an average received pressure level of 173 dB re 1 microPa on an 
(approximate) rms basis, and that 10 percent of feeding whales 
interrupted feeding at received levels of 163 dB. Those findings were 
generally consistent with the results of experiments conducted on 
larger numbers of gray whales that were migrating along the California 
coast, and on observations of Western Pacific gray whales feeding off 
Sakhalin Island, Russia (Johnson, 2002).
    Data on short-term reactions (or lack of reactions) of cetaceans to 
impulsive noises do not necessarily provide information about long-term 
effects. It is not known whether impulsive noises affect reproductive 
rate or distribution and habitat use in subsequent days or

[[Page 32050]]

years. However, gray whales continued to migrate annually along the 
west coast of North America despite intermittent seismic exploration 
and much ship traffic in that area for decades (Malme et al., 1984). 
Bowhead whales continued to travel to the eastern Beaufort Sea each 
summer despite seismic exploration in their summer and autumn range for 
many years (Richardson et al., 1987). Populations of both gray whales 
and bowhead whales grew substantially during this time. In any event, 
the brief exposures to sound pulses from the proposed airgun source are 
highly unlikely to result in prolonged effects.
Toothed Whales
    Little systematic information is available about reactions of 
toothed whales to noise pulses. Few studies similar to the more 
extensive baleen whale/seismic pulse work previously summarized (and 
discussed in more detail in Appendix C of GXT's IHA application) have 
been reported for toothed whales. However, systematic work on sperm 
whales is underway (Tyack et al., 2003), and there is an increasing 
amount of information about responses of various odontocetes to seismic 
surveys based on monitoring studies (e.g., Stone, 2003; Smultea et al., 
2004; Moulton and Miller, in press).
    Seismic operators and marine mammal observers sometimes see 
dolphins and other small toothed whales near operating airgun arrays, 
but in general there seems to be a tendency for most delphinids to show 
some limited avoidance of seismic vessels operating large airgun 
systems. However, some dolphins seem to be attracted to the seismic 
vessel and floats, and some ride the bow wave of the seismic vessel 
even when large arrays of airguns are firing. Nonetheless, there have 
been indications that small toothed whales sometimes move away, or 
maintain a somewhat greater distance from the vessel, when a large 
array of airguns is operating than when it is silent (e.g., Goold, 
1996a,b,c; Calambokidis and Osmek, 1998; Stone 2003). The beluga may be 
a species that (at least at times) shows long-distance avoidance of 
seismic vessels. Aerial surveys during seismic operations in the 
southeastern Beaufort Sea recorded much lower sighting rates of beluga 
whales within 10-20 km of an active seismic vessel. These results were 
consistent with the low number of beluga sightings reported by 
observers aboard the seismic vessel, suggesting that some belugas might 
be avoiding the seismic operations at distances of 10-20 km (6.2-12.4 
mi)(Miller et al., 2005).
    Captive bottlenose dolphins and (of more relevance in this project) 
beluga whales exhibit changes in behavior when exposed to strong pulsed 
sounds similar in duration to those typically used in seismic surveys 
(Finneran et al., 2002, 2005). However, the animals tolerated high 
received levels of sound (pk-pk level >200 dB re 1 microPa) before 
exhibiting aversive behaviors. With the presently-planned seismic 
source, such levels would be limited to distances less than 200 m (656 
ft) of the 36-airgun array in shallow water. The reactions of belugas 
to the GXT survey are likely to be more similar to those of free-
ranging belugas exposed to airgun sound (Miller et al., 2005) than to 
those of captive belugas exposed to a different type of strong 
transient sound (Finneran et al., 2000, 2002).
    Odontocete reactions to large arrays of airguns are variable and, 
at least for delphinids, seem to be confined to a smaller radius than 
has been observed for mysticetes (see GXT IHA Application, Apppendix 
C).
Pinnipeds
    Pinnipeds are not likely to show a strong avoidance reaction to the 
airgun sources that will be used. Visual monitoring from seismic 
vessels has shown only slight (if any) avoidance of airguns by 
pinnipeds, and only slight (if any) changes in behavior (see GXT's IHA 
Application, Appendix C). Ringed seals frequently do not avoid the area 
within a few hundred meters of operating airgun arrays (Harris et al., 
2001; Moulton and Lawson, 2002; Miller et al., 2005). However, initial 
telemetry work suggests that avoidance and other behavioral reactions 
by two other species of seals to small airgun sources may at times be 
stronger than evident to date from visual studies of pinniped reactions 
to airguns (Thompson et al., 1998). Even if reactions of the species 
occurring in the present study area are as strong as those evident in 
the telemetry study, reactions are expected to be confined to 
relatively small distances and durations, with no long-term effects on 
pinniped individuals or populations.
Strandings and Mortality
    Marine mammals close to underwater detonations of high explosives 
can be killed or severely injured, and the auditory organs are 
especially susceptible to injury (Ketten et al., 1993; Ketten, 1995). 
Airgun pulses are less energetic and have slower rise times, and there 
is no evidence that they can cause serious injury, death, or stranding 
even in the case of large airgun arrays. However, the association of 
mass strandings of beaked whales with several naval exercises using 
mid-frequency tactical sonar and, in one case, a scientific seismic 
survey, has raised the possibility that beaked whales exposed to strong 
pulsed sounds may be especially susceptible to injury and/or behavioral 
reactions that can lead to stranding. Appendix C in GXT's application 
provides additional details.
    Seismic pulses and mid-frequency sonar pulses are quite different. 
Sounds produced by airgun arrays are broadband with most of the energy 
below 1 kHz. Typical military mid-frequency sonars operate at 
frequencies of 2-10 kHz, generally with a relatively narrow bandwidth 
at any one time and are directed horizontally, not directly downward as 
is the case with seismic arrays. Thus, it is not appropriate to assume 
that there is a direct connection between the effects of military sonar 
and seismic surveys on marine mammals. .
    In September, 2002, there was a stranding of two Cuvier's beaked 
whales in the Gulf of California, Mexico, when the research vessel 
Maurice Ewing was operating a 20 airgun, 8490 in\3\ array in the 
general area. The link between the stranding and the seismic surveys 
was inconclusive and not based on any physical evidence (Hogarth, 2002; 
Yoder, 2002). Nonetheless, that incident plus the incidents involving 
beaked whale strandings near naval exercises suggests a need for 
caution in conducting seismic surveys in areas occupied by beaked 
whales. However, no beaked whales are found within the GXT project area 
and the planned monitoring and mitigation measures are expected to 
minimize any possibility for mortality of other species.

Potential Effects of Pinger Signals on Marine Mammals

    A pinger system (DigiRANGE I and II, Input/Output, Inc.) will be 
used during seismic operations to position the airgun array and 
hydrophone streamer relative to the vessel. Sounds from the pingers are 
very short pulses, occurring for 10 ms, with source level approximately 
180 dB re 1 microPa @ 1 m at 55 kHz, approximately 188 dB re microPa @ 
1 m at 75 kHz, and approximately 184 dB re 1 microPa @ 1 m at 95 kHz. 
One pulse is emitted on command from the operator aboard the source 
vessel, which under normal operating conditions is approximately once 
every 10 sec. Most of the energy in the sound pulses emitted by this 
pinger is at very high frequencies between 50 and 100 kHz. The signal 
is omnidirectional.
    The pinger produces sounds that are above the range of frequencies 
produced

[[Page 32051]]

or heard by many of the marine mammals expected to occur in the study 
area. However, the beluga whale produces echolocation sounds (clicks) 
within the 50-100 kHz range (Au et al., 1985, 1987; Au, 1993), and 
belugas have good hearing sensitivity across this ultrasonic frequency 
band (White et al., 1978; Johnson et al., 1989). In the event that 
killer whales or harbor porpoises are encountered, they could also hear 
the pinger signals. Some seals also can hear sounds at frequencies up 
to somewhat above 55 kHz. Baleen whales would not hear sounds at and 
above 55 kHz.
Masking
    Marine mammal communications will not be masked appreciably by the 
pinger signals. This is a consequence of the relatively low power 
output, low duty cycle, and brief period when an individual mammal is 
likely to be within the area of potential effects. Also, in the case of 
seals, the pulses do not overlap with the predominant frequencies in 
the calls, which would avoid significant masking. As baleen whales 
would not hear sounds at and above 55 kHz, the pinger would have no 
effect on them.
Behavioral Responses
    Marine mammal behavioral reactions to other pulsed sound sources 
are discussed under seismic impacts, and responses to the pinger are 
likely to be similar to those for other pulsed sources if received at 
the same levels. However, the pulsed signals from the pinger are much 
weaker than those from airguns. Therefore, behavioral responses are not 
expected unless marine mammals are very close to the source. In GXT's 
project, odontocetes and seals are the types of marine mammals that 
might hear the pings if these animals were close to the source. The 
maximum reaction that might be expected would be a startle reaction or 
other short-term response.
Hearing Impairment and Other Physical Effects
    As source levels of the pinger are much lower than those of the 
airguns, it is unlikely that the pinger produces pulse levels strong 
enough to cause temporary hearing impairment or (especially) physical 
injuries even in an animal that is (briefly) in a position near the 
source.

Potential Numbers of Marine Mammals that Might be Exposed to Sound 
Pressure Levels of 160 dB and Higher (Level B Harassment)

    The methodology used, and the assumptions made, by GXT to estimate 
incidental take by Level B harassment, at sound pressure levels at 160 
dB or above, by seismic and the numbers of marine mammals that might be 
affected during the proposed seismic survey area in the Chukchi Sea are 
presented in the GXT application. This document provides here the 
estimates of the number of potential sound exposure to levels 160 dB re 
1 microPa (rms) or greater. While GXT believes, based on the evidence 
summarized in the application, that the 170-dB criterion is considered 
appropriate for estimating Level B harassment for delphinids and 
pinnipeds, which tend to be less responsive (whereas the 160-dB 
criterion is considered relevant for other cetaceans), NMFS has noted 
in the past that there is no empirical evidence to indicate that some 
delphinid species do not respond at the lower level (i.e., 160 dB). 
Also, since delphinids are not found in the Chukchi Sea, this suggested 
new criterion is irrelevant for this action. While the application 
cites recent empirical information regarding responses of pinnipeds to 
low-frequency seismic sounds, the information cited in the application 
is less than convincing. As a result, NMFS proposes to continue to use 
the 160-dB isopleth to estimate the numbers of pinnipeds that may be 
taken by Level B harassment, but has also shown the estimated numbers 
of pinnipeds that might be taken at the higher SPL of 170 dB. However, 
while some autumn migrating bowheads in the Beaufort Sea have been 
found to react to a noise threshold closer to 130 dB re 1 microPa (rms; 
Miller et al., 1999; Richardson et al., 1999), evidence in Richardson 
et al. (1986) and Miller et al. (2005) indicate that the 160-dB 
criterion is suitable for summering bowhead whales.
    The following estimates are based on a consideration of the number 
of marine mammals that might be disturbed appreciably by about 5302 
line-km (3294 mi) of seismic surveys across the Chukchi Sea. An assumed 
total of 6628 km (4118 mi) of trackline in the Chukchi Sea includes a 
25 percent allowance over and above the planned trackline to allow for 
turns and lines that might have to be repeated because of poor data 
quality, or for minor changes to the survey design.
    The anticipated radii of influence of the pinger system are much 
less than those for the airgun array (for those species that can hear 
it). It is assumed that, during simultaneous operations of the airgun 
array and pinger system, any marine mammals close enough to be affected 
by the pingers would already be affected by the airguns. However, 
whether or not the airguns are operating simultaneously with the pinger 
system, odontocetes and seals are expected to exhibit no more than 
momentary and inconsequential responses to the pingers, similar to 
reactions from the pingers on the thousands of maritime private and 
commercial vessels using similar instrumentation for obtaining 
bathymetric information. Such reactions are not considered to 
constitute ``taking'' (NMFS, 2001). Therefore, no additional allowance 
is included for animals that might be affected by sound sources other 
than the airguns.
    The estimates of marine mammals that might be present and, 
therefore, potentially disturbed are based on available data about 
mammal distribution and densities at different locations and times of 
the year. The proposed survey covers a large area in the Chukchi Sea in 
two different seasons. The estimates of marine mammal densities have 
therefore been separated both spatially and temporarily in an attempt 
to represent the distribution of animals expected to be encountered 
over the duration of the survey. Density estimates in the Chukchi Sea 
have been derived for two time periods, the early summer period 
covering the months of June and July (Table 3 in GXT's IHA 
application), and the late fall period including most of October and 
November (Table 4 in GXT's IHA application). For the Chukchi Sea, 
cetacean densities during the summer were estimated from effort and 
sighting data in Moore et al. (2000) and Richardson and Thomson (eds., 
2002), while pinniped densities were estimated from Bengtson (2005) and 
Moulton and Lawson (2002).
    The potential number of events when members of each species might 
be exposed to received levels 160 dB re 1 microPa (rms) or greater was 
calculated by summing the results for each season and habitat zone by 
multiplying:
    (1) The expected species density, either ``average'' (i.e., best 
estimate) or ``maximum'' (see Tables 3 and 4 in GXT's IHA application),
    (2) The anticipated total line-kilometers of operations with the 
36-airgun array in the time period, and habitat zone to which that 
density applies after applying a 25 percent allowance for possible 
additional line kilometers (see GXT IHA application) and

[[Page 32052]]

    (3) The cross-track distances within which received sound levels 
are predicted to be [gteqt]160 (Table 1 in this document).
    Some marine mammals that are estimated to be exposed, particularly 
migrating bowhead whales, might show avoidance reactions before being 
exposed to 160 dB re 1 microPa (rms). Thus, these calculations actually 
estimate the number of exposures to [gteqt]160 dB that would occur if 
there were no avoidance of the area ensonified to that level.
    For the 36-airgun array, the cross track distance is 2X the 
predicted 160-dB radius predicted by the Gundalf model or 6000 m (19685 
ft). Applying the approach described above, 55,560 km\2\ of open-water 
habitat in the Chukchi Sea would be within the 160-dB isopleth over the 
course of the seismic project. After adding the 25 percent contingency 
to the expected number of line kilometers of seismic run, the number of 
exposures is calculated based on 69,450 km\2\.
    The numbers of exposures in the two habitat categories (open water 
and ice margin) were then summed for each species. GXT's estimate of 
marine mammal exposures to SPL of 160 dB (and greater) is provided in 
Tables 5, 6, and 7 in the IHA application. Table 2 in this document is 
a summary of that information.

[[Page 32053]]

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[[Page 32054]]

    GXT estimates that bowhead, beluga, and gray whales are the only 
cetaceans expected to be exposed to noise levels [gteqt]160-dB levels. 
The estimates show that one endangered cetacean species (the bowhead 
whale) is expected to be exposed to such noise levels, unless bowheads 
avoid the approaching survey vessel before the received levels reach 
160 dB. Migrating bowheads are likely to do so, though summering 
bowheads, if encountered may not. For convenience, GXT refers to either 
eventuality as an ``exposure''. As a result, GXT's average and maximum 
estimates for bowhead whale exposures are 59 and 337, respectively 
(Table 2). The average and maximum estimates of the number of exposures 
of cetaceans are beluga (163 and 650) and gray whale (84 and 337). The 
seasonal breakdown of these numbers is shown in Tables 5 and 6 and 
totaled in Table 7 in the application and Table 2 in this document. 
Other cetacean species may occasionally occur near the seismic areas, 
but given their low estimated densities in the area, they are not 
likely to be exposed to SPLs of 160 dB or greater.
    The ringed seal is the most widespread and abundant pinniped in 
ice-covered arctic waters, but there is a great deal of annual 
variation in population size and distribution of these marine mammals. 
Ringed seals account for the vast majority of marine mammals expected 
to be encountered, and, therefore, exposed to airgun sounds with 
received levels [gteqt]160 dB re 1 microPa (rms) during the proposed 
seismic survey. Haley and Ireland (2006) reported that 20 percent of 
ringed seals remained on the ice when a seismic vessel passed. Because 
the SPL radii for this project are assumed to be larger than those 
found in the Haley and Ireland (2006) project, GXT believes a larger 
percent of ringed seals within the 160-dB radii are likely to remain on 
the ice while the M/V Discoverer II passes. Therefore, GXT's estimates 
of numbers of ringed seals that might be exposed to sound levels 160 dB 
re 1 microPa (rms) were reduced by 50 percent to account for animals 
that are expected to be out of the water, and hence exposed to much 
lower levels of seismic sounds. The average (and maximum) estimate is 
that 3056 (max. 12,223) ringed seals out of a Beaufort/Chukchi Sea 
population of 245,048 seals might be exposed to seismic sounds with 
received levels >160 dB. This assumes as many as 50 percent of seals 
encountered in the ice margin will be hauled out on ice and not exposed 
to seismic sounds.
    However, GXT believes that pinnipeds are not likely to react to 
seismic sounds unless the received levels are [gteqt]170 dB re 1 
microPa (rms), and many of those exposed to 170 dB also will not react 
overtly (Harris et al., 2001; Moulton and Lawson, 2002; Miller et al., 
2005). In any event, the best and maximum estimates of numbers of 
ringed seals that might be exposed to sounds [gteqt]170 dB are 514 and 
2493, respectively, if 50 percent of ringed seals encountered in the 
ice margin were in or entered the water (see Table 7 in GXT's IHA 
application).
    Two other species of pinnipeds are expected to be encountered 
during the proposed seismic survey. With Alaskan stock estimates of 
300-450,000 and 1000 respectively, the bearded seal has average and 
maximum exposure estimates of 1776 and 7104, and the spotted seal has 
average and maximum exposure estimates of 17 and 70, respectively. 
Finally, the harbor seal is unlikely to be encountered so no exposure 
estimates have been made.

Effects of Seismic Noise and Other Activities on Subsistence Uses

    GXT (2006) reports that marine mammals are legally hunted in 
Alaskan waters by coastal Alaska Natives; species hunted include 
bowhead and beluga whales; ringed, spotted, and bearded seals; 
walruses, and polar bears. The importance of each of the various 
species varies among the communities based largely on availability. 
Bowhead whales, belugas, and walruses are the marine mammal species 
primarily harvested during the time of the proposed seismic survey. 
There is little or no bowhead hunting by the community of Point Lay, so 
beluga and walrus hunting are of more importance there. Members of the 
Wainwright community do hunt bowhead whales in the spring, although 
bowhead whale hunting conditions there are often more difficult than 
elsewhere, and traditionally they do not hunt bowheads during seasons 
when GXT's seismic operation would occur. Depending on the level of 
success during the spring bowhead hunt, Wainwright residents may be 
very dependent on the presence of belugas in a nearby lagoon system 
during July and August. Barrow residents focus hunting efforts on 
bowhead whales during the spring and generally do not hunt beluga then. 
Barrow residents also hunt in the fall.
    Bowhead whale hunting is the key activity in the subsistence 
economies of Barrow and Wainwright. The whale harvests have a great 
influence on social relations by strengthening the sense of Inupiat 
culture and heritage in addition to reinforcing family and community 
ties.
    An overall quota system for the hunting of bowhead whales was 
established by the International Whaling Commission in 1977. The quota 
is now regulated through an agreement between NMFS and the Alaska 
Eskimo Whaling Commission (AEWC). The AEWC allots the number of bowhead 
whales that each whaling community may harvest annually (USDI/BLM, 
2005).
    Bowhead whales migrate around northern Alaska twice each year, 
during the spring and autumn, and are hunted in both seasons. Bowhead 
whales are hunted from Wainwright only during the spring migration and 
animals are not successfully harvested every year. The spring hunt 
there and at Barrow occurs after leads open due to the deterioration of 
pack ice; the spring hunt typically occurs from early April until the 
first week of June. The fall migration of bowhead whales that summer in 
the eastern Beaufort Sea typically begins in late August or September. 
Fall migration into Alaskan waters is primarily during September and 
October. However, in recent years a small number of bowheads have been 
seen or heard offshore from the Prudhoe Bay region during the last week 
of August (Treacy, 1993; LGL and Greeneridge, 1996; Greene, 1997; 
Greene et al., 1999; Blackwell et al., 2004).
    The location of the fall subsistence hunt near Barrow depends on 
ice conditions and (in some years) industrial activities that influence 
the bowheads movements as they move west (Brower, 1996). In the fall, 
subsistence hunters use aluminum or fiberglass boats with outboards. 
Hunters prefer to take bowheads close to shore to avoid a long tow 
during which the meat can spoil, but Braund and Moorehead (1995) report 
that crews may (rarely) pursue whales as far as 80 km (50 mi). The 
autumn hunt usually begins in Barrow in mid-September, and mainly 
occurs in waters east and northeast of Point Barrow. The whales have 
usually left the Beaufort Sea by late October (Treacy, 2002a,b).
    The scheduling of this seismic survey has been discussed with 
representatives of those concerned with the subsistence bowhead hunt, 
most notably the AEWC, the Barrow Whaling Captains' Association, and 
the North Slope Borough (NSB) Department of Wildlife Management.
    The planned starting date for seismic surveys in the Chukchi Sea 
(about July 10) is well after the end of the spring bowhead migration 
and hunt at Wainwright and Barrow. Similarly, the resumption of seismic 
activities in the Chukchi Sea in October will occur after most 
subsistence whaling from Barrow

[[Page 32055]]

has been completed and if the hunt is still active, seismic operations 
will be conducted far from Barrow to avoid conflicting with subsistence 
hunting activities.
    Beluga whales are available to subsistence hunters along the coast 
of Alaska in the spring when pack-ice conditions deteriorate and leads 
open up. Belugas may remain in coastal areas or lagoons through June 
and sometimes into July and August. The community of Point Lay is 
heavily dependent on the hunting of belugas in Kasegaluk Lagoon for 
subsistence meat. From 1983-1992 the average annual harvest was about 
40 whales (Fuller and George, 1997). In Wainwright and Barrow, hunters 
usually wait until after the spring bowhead whale hunt is finished 
before turning their attention to hunting belugas. The average annual 
harvest of beluga whales taken by Barrow for 1962-1982 was five (MMS, 
1996). The Alaska Beluga Whale Committee recorded that 23 beluga whales 
were harvested by Barrow hunters from 1987 to 2002, ranging from 0 in 
1987, 1988 and 1995 to the high of 8 in 1997 (Fuller and George, 1997; 
Alaska Beluga Whale Committee, 2002 in USDI/BLM, 2005). GXT states that 
it is possible, but unlikely, that accessibility to belugas during the 
subsistence hunt could be impaired during the survey. However, very 
little of the proposed survey is within 25 km (15.5 mi) of the Chukchi 
coast. That means the vessel will usually be well offshore away from 
areas where seismic surveys would influence beluga hunting by these 
communities.
    Because seals (ringed, spotted, bearded) are hunted in nearshore 
waters and the seismic survey will remain offshore of the coastal and 
nearshore areas of these seals, seismic surveys should not conflict 
with harvest activities.

Impact on Habitat

    GXT states that the proposed seismic survey will not result in any 
permanent impact on habitats used by marine mammals, or to the food 
sources they utilize. Although feeding cetaceans and pinnipeds may 
occur in the area, the proposed activities will be of short duration in 
any particular area at any given time; thus any effects would be 
localized and short-term.
    One of the reasons for the adoption of airguns as the standard 
energy source for marine seismic surveys was that, unlike explosives, 
they do not result in any appreciable fish kill. However, the existing 
body of information relating to the impacts of seismic on marine fish 
and invertebrate species, the primary food sources of pinnipeds and 
belugas, is very limited.
    In water, acute injury and death of organisms exposed to seismic 
energy depends primarily on two features of the sound source: (1) the 
received peak pressure, and (2) the time required for the pressure to 
rise and decay (Hubbs and Rechnitzer, 1952; Wardle et al., 2001). 
Generally, the higher the received pressure and the less time it takes 
for the pressure to rise and decay, the greater the chance of acute 
pathological effects. Considering the peak pressure and rise/decay time 
characteristics of seismic airgun arrays used today, the pathological 
zone for fish and invertebrates would be expected to be within a few 
meters of the seismic source (Buchanan et al., 2004).
    Therefore, NMFS has preliminarily determined that the proposed 
Chukchi Sea seismic program for 2006 will have negligible to low 
physical effects on the various life stages of fish and invertebrates 
or have any habitat-related effects that could cause significant or 
long-term consequences for individual marine mammals or their 
populations, since operations at any specific location will be limited 
in duration.

Proposed Mitigation Measures

    For the proposed seismic survey in the Chukchi Sea, GXT proposes to 
deploy an airgun source composed of 36 sleeve airguns. The airguns 
comprising the array will be spread out horizontally, so that most the 
energy will be directed downward. GXT believes that the directional 
nature of this array is an important mitigating factor. This 
directionality will result in reduced sound levels at any given 
horizontal distance compared to levels expected at that distance if the 
source were omnidirectional with the stated nominal source.
    Important mitigation factors built into the design of the survey 
include the fact that the spring migration and hunt for bowhead whales 
in Chukchi waters will be completed prior to the start of the survey. 
Also, it is likely that many bowhead whales have already reached 
Russian waters north of the Chukotsk Peninsula when surveying is 
expected to resume in the autumn. Thus, the density of bowhead whales 
encountered during the fall in the Chukchi Sea, where the migration 
corridor becomes bifurcated and broad, is expected to be much lower 
than that of the Beaufort Sea during the fall, where the migration 
corridor is narrow (Richardson and Thomson, 2002).
    Received sound fields were modeled by GXT for the 36-airgun 
configuration, in relation to distance and direction from the array. 
The distance from the array by which received levels would have 
diminished to 190, 180, 160 and other levels (in dB re 1 microPa rms) 
are likely to depend on water depth and location. Table 1 presents the 
predicted sound radii for the 36-airgun array in intermediate (200-500 
m (656-1640 ft)) water depths. The radii for deeper or shallower water 
are predicted by GXT to be smaller than those for intermediate depths.
    Empirical data concerning these radii are not yet available, but 
will be acquired early in the 2006 field season. In addition to 
performing an acoustic characterization/verification of the full 36-
airgun array at different depths, the output from a single 40 in\3\ 
sleeve gun source will also be measured in order to determine the 
appropriate safety radius for use during power downs. A summary report 
on the acoustic measurements and proposed refinements to the safety 
radii will be made available for review shortly after the data have 
been collected. Until these empirical data are available, the radii 
predicted to be applicable to intermediate water depths (with a 
precautionary 1.5X adjustment) will also be applied for deep and 
shallow water operations when estimating the required safety radii. 
More detailed modeling of the airgun array may be completed prior to 
the beginning of the field season and the resulting 180 and 190 dB 
(rms) safety radii (with 1.5X factor) will be applied at the start of 
the season if that occurs.
    The following mitigation measures, as well as marine mammal visual 
monitoring (discussed later in this document), will be implemented for 
the subject seismic surveys: (1) Speed and course alteration (provided 
that they do not compromise operational safety requirements); (2) 
power-down/shut-down procedures; and (3) ramp-up procedures.

Speed and Course Alteration

    If a marine mammal is detected outside its respective safety zone 
(180 dB for cetaceans, 190 dB for pinnipeds) and, based on its position 
and the relative motion, is likely to enter the safety zone, the 
vessel's speed and/or direct course may, when practical and safe, be 
changed to avoid the mammal in a manner that also minimizes the effect 
to the planned science objectives. The marine mammal activities and 
movements relative to the seismic vessel will be closely monitored to 
ensure that the marine mammal does not approach within the safety zone. 
If the mammal appears likely to enter the safety zone, further 
mitigative actions will be taken

[[Page 32056]]

(i.e., either further course alterations or shut down of the airguns).

Power-down and Shut-down Procedures

    A power-down involves decreasing the number of airguns in use such 
that the radii of the 190-dB and 180-dB zones are decreased to the 
extent that observed marine mammals are not in the applicable safety 
zone. A power-down may also occur when the vessel is moving from one 
seismic line to another. During a power-down, one airgun (or some other 
number of airguns less than the full airgun array) is operated. The 
continued operation of one airgun is intended to (a) alert marine 
mammals to the presence of the seismic vessel in the area, and (b) 
retain the option of initiating a ramp up to full operations under poor 
visibility conditions. In contrast, a shut-down occurs when all airgun 
activity is suspended.
    If a marine mammal is detected outside the safety radius but 
appears likely to enter the safety radius, and if the vessel's speed 
and/or course cannot be changed to avoid having the mammal enter the 
safety radius, the airguns may (as an alternative to a complete shut 
down) be powered down before the mammal is within the safety radius. 
Likewise, if a mammal is already within the safety zone when first 
detected, the airguns will be powered down immediately if this is a 
reasonable alternative to a complete shut down. During a power-down of 
the 36-airgun array, the number of guns operating will be reduced to a 
single 40 in\3\ sleeve airgun. The 190-dB (rms) safety radius around 
the power down source has not yet been estimated, but will be estimated 
before the field season and verified during acoustic verification 
measurements made at the start of seismic operations. If a marine 
mammal is detected within or near the smaller safety radius around the 
single 40 in\3\ sleeve airgun, all airguns will be shut down.
    Following a power-down, operation of the full airgun array will not 
resume until the marine mammal has cleared the safety zone. The animal 
will be considered to have cleared the safety zone if it is visually 
observed to have left the safety zone, or has not been seen within the 
zone for 15 minutes in the case of small odontocetes and pinnipeds, or 
has not been seen within the zone for 30 minutes in the case of 
mysticetes (large odontocetes do not occur within the activity area).

Shut-down Procedures

    The operating airgun(s) will be shut down completely if a marine 
mammal approaches or enters the applicable safety radius and a power-
down is not practical or adequate to reduce exposure to less than 190 
or 180 dB (rms), as appropriate. The operating airgun(s) will also be 
shut down completely if a marine mammal approaches or enters the 
estimated safety radius around the reduced source (one 40 in3 sleeve 
gun) that will be used during a power down.
    Airgun activity will not resume until the marine mammal has cleared 
the safety radius. The animal will be considered to have cleared the 
safety radius as described previously. Ramp-up procedures will be 
followed during resumption of full seismic operations.

Ramp-up Procedure

    A ``ramp-up'' or ``soft start'' procedure will be followed when the 
airgun array begins operating after a specified-duration period with no 
or reduced airgun operations. The specified period depends on the speed 
of the source vessel, the size of the airgun array that is being used, 
and the size of the safety radii, but is often about 10 minutes or the 
time the vessel would reach the location of the 180-dB radius at the 
time of shut-down or power-down, whichever is greater.
    NMFS normally requires that, once ramp up commences, the rate of 
ramp-up be no more than 6 dB per 5 min period. Ramp-up will likely 
begin with a single airgun (the smallest, or 40 in\3\). The precise 
ramp-up procedure will be determined prior to start-up (based upon 
array configuration), but will follow NMFS' guideline with a ramp-up 
rate of no more than 6 dB per 5 min period. The standard industry 
procedure is to double the number of operating airguns at 5-minute 
intervals which is equal to about a 6 dB increase. During the ramp-up, 
the safety zone for the full 36-airgun array (or whatever smaller 
source might then be in use) will be maintained. If the complete 180-dB 
safety radius has not been visible for at least 30 minutes prior to the 
planned start of a ramp-up in either daylight or nighttime, ramp up 
will not commence unless at least one airgun has been operating during 
that period. This means that it will not be permissible to ramp up the 
36-airguns from a complete shut down in thick fog when the entire 180-
dB safety zone is not visible. If the entire safety radius is visible 
using vessel lights and/or night-vision devices (NVDs), then start up 
of the airguns from a complete shut down may occur at night. If one 
airgun has operated during a power-down period, ramp up to full power 
will be permissible at night or in poor visibility, on the assumption 
that marine mammals will either be alerted by the sounds from the 
single airgun and could move away, or may be detected by visual 
observations. Given the responsiveness of bowhead and beluga whales to 
airgun sounds, it can be assumed that those species, in particular, 
will move away during a ramp up. There have been direct observations of 
bowheads moving away when a single airgun begins to operate (Richardson 
et al., 1986; Ljungblad et al., 1988).
    Ramp-up of the airguns will not be initiated during the day or at 
night if a marine mammal has been sighted within or near the applicable 
safety radius during the previous 15 minutes.

Mitigation for Subsistence Needs

    GXT is completing negotiations on a Plan of Cooperation (POC)(also 
called a Conflict Avoidance Agreement (CAA)) for the proposed 2006 
seismic survey in the Chukchi Sea, in consultation with representatives 
of communities along the Alaska coast including Pt. Hope, Pt. Lay, 
Wainwright, and Barrow. GXT is working with the people of these 
communities to identify and avoid areas of potential conflict, and 
provided a presentation at the AEWC mini-convention in Anchorage, AK, 
on March, 15 2006. Meetings with AEWC and NSB representatives also 
occurred at the time of the convention, and further communication is 
ongoing leading toward adoption of a POC/CAA. Also, GXT participated in 
the open water peer/stakeholder review meeting that was convened by 
NMFS in Anchorage on April 18-21, 2006, along with representatives of 
the AEWC and NSB.
    The POC/CAA will cover the phases of GXT's seismic survey planned 
to occur in the Beaufort and Chukchi seas between July 1 and November 
30, 2006. The purpose will be to identify measures that will be taken 
to minimize any adverse effects on the availability of marine mammals 
for subsistence uses, and to ensure good communication between GXT 
(including the project leaders and the M/V Discoverer II), native 
communities along the coast, and subsistence hunters at sea.
    Subsequent meetings with whaling captains, other community 
representatives, the AEWC, NSB, and any other parties to the POC/CAA 
will be held as necessary to negotiate the terms of the POC/CAA and to 
coordinate the planned seismic survey operation with subsistence 
hunting activity.
    The proposed POC/CAA may address the following: (1) operational 
agreement and communications procedures; (2) where/when agreement 
becomes

[[Page 32057]]

effective; (3) general communications scheme; (4) on-board Inupiat 
observer; identification of seasonally sensitive areas; (5) vessel 
navigation; (6) air navigation; (7) marine mammal monitoring 
activities; (8) measures to avoid impacts to marine mammals; (9) 
measures to avoid conflicts in areas of active whaling; (10) emergency 
assistance; and (11) dispute resolution process.
    In the unlikely event that subsistence hunting or fishing is 
occurring within 5 km (3 mi) of the M/V Discoverer II's trackline, or 
in other situations inconsistent with the CAA, the airgun operations 
will be suspended until the vessel is greater than 5 km (3 mi) away and 
otherwi