[Federal Register Volume 64, Number 112 (Friday, June 11, 1999)]
[Notices]
[Pages 31548-31553]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-14902]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration
[I.D. 021699A]


Small Takes of Marine Mammals Incidental to Specified Activities; 
Seismic Hazards Investigation in Southern California

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

ACTION: Notice of issuance of an incidental harassment authorization.

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SUMMARY: In accordance with provisions of the Marine Mammal Protection 
Act (MMPA) as amended, notification is hereby given that an Incidental 
Harassment Authorization (IHA) to take small numbers of marine mammals 
by harassment incidental to collecting marine seismic-reflection data 
offshore from southern California has been issued to the U.S. 
Geological Survey (USGS).

DATES: This authorization is effective from June 3, 1999, through July 
31, 1999.

ADDRESSES: A copy of the application may be obtained by writing to 
Donna Wieting, Acting Chief, Marine Mammal 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.

FOR FURTHER INFORMATION CONTACT: Kenneth R. Hollingshead, NMFS, (301) 
713-2055, or Christina Fahy, NMFS, 562-980-4023.

SUPPLEMENTARY INFORMATION:

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
directs the Secretary of Commerce 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) 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.
    Permission may 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 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.''
    Subsection 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. The MMPA now defines ``harassment'' as:

     ...any act of pursuit, torment, or annoyance which
    (a) has the potential to injure a marine mammal or
    marine mammal stock in the wild; or (b) 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.

    Subsection 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 
small numbers 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 January 15, 1999, NMFS received a request from the USGSfor 
authorization to take small numbers of several species of marine 
mammals by harassment incidental to collecting marine seismic-
reflection data offshore from southern California. Seismic data was 
planned to be collected during a 2-week period between May and July 
1999 to support studies of the regional landslide and earthquake 
hazards and to understand how saltwater invades coastal aquifers. A 
revised request was received on February 11, 1999.

Background

    The USGS proposes to conduct a high-resolution seismic survey 
offshore from Southern California to investigate (1) the hazards posed 
by landslides and potential earthquake faults in the nearshore region 
from Santa Barbara to San Diego and (2) the invasion of seawater into 
freshwater aquifers that are critical to the water supply for people 
within the Los Angeles-San Pedro area. Both of these tasks are multi-
year efforts that require using a small airgun.
    Coastal Southern California is the most highly populated urban area 
along the U.S. Pacific coast. The primary objective of the USGS 
research is to provide information to help mitigate the earthquake 
threat to this area. The USGS emphasizes that the goal is not 
earthquake prediction but rather an assistance in determining what 
steps might be taken to minimize the devastation should a large quake 
occur. The regional earthquake threat is known to be high, and a major 
earthquake could adversely affect the well being of a large number of 
people.
    Important geologic information that the USGS will derive from this 
project's seismic-reflection data concerns how earthquake deformation 
is distributed offshore; that is, where the active faults are and what 
the history of movement along them has been. This should improve 
understanding of the shifting pattern of deformation that occurred

[[Page 31549]]

over both the long term (approximately the last 100,000 years) and 
short term (the last few thousand years). The USGS seeks to identify 
actively deforming structures that may constitute significant 
earthquake threats. The USGS also proposes to locate offshore 
landslides that might affect coastal areas. Not only major subsea 
landslides might affect the footings of coastal buildings, but also 
very large slides can generate local tsunamis. These large sea waves 
can be generated by seafloor movement that is produced either by 
landslides or by earthquakes. Knowing where large slides have occurred 
offshore will help locate areas susceptible to wave inundation.
    Some faults that have produced earthquakes lie entirely offshore or 
extend into offshore areas where they can be studied using high-
resolution seismic-reflection techniques. An example is the Rose Canyon 
fault, which, extending through the San Diego area, is considered to be 
the primary earthquake threat. This fault extends northward from La 
Jolla, beneath the inner continental shelf, and appears again onshore 
in the Los Angeles area. This fault and others like it near shore could 
generate moderate (M5-6) to large (M6-7) earthquakes.
    Knowing the location and geometry of fault systems is critical to 
estimating the location and severity of ground shaking. Therefore, the 
results of this project will contribute to decisions involving land 
use, hazard zonation, insurance premiums, and building codes.
    The proposed work is in collaboration with scientists at the 
Southern California Earthquake Center, which analyzes faults and 
earthquakes in onshore regions, and with scientists at the Scripps 
Institute of Oceanography, who measure strain (incremental movement) on 
offshore faults.
    The USGS also wants to collect high-resolution seismic- reflection 
data to locate the sources and pathways of seawater that intrudes into 
freshwater aquifers below San Pedro. Ground water usage in the Los 
Angeles basin began in the mid-1800s. Today, more than 44,000 acre-feet 
of freshwater each year are extracted from the aquifers that underlie 
just the city of San Pedro. Extracting freshwater from coastal aquifers 
causes offshore salt water to flow toward areas of active pumping. To 
limit this salt-water intrusion, the Water Replenishment District and 
water purveyors in San Pedro are investing $2.7 million per year to 
inject freshwater underground to establish a zone of high water 
pressure in the aquifer. The resulting zone of high pressure will form 
a barrier between the invasive saltwater and the productive coastal 
aquifers.
    USGS scientists in San Diego are working with the Los Angeles 
County Department of Public Works and the Water Replenishment District 
to develop a ground-water simulation model to predict fluid flow below 
San Pedro and nearby parts of the Los Angeles Basin. This model will 
eventually be used in managing water resources. The accuracy of the 
present model, however, is compromised by a paucity of information 
about aquifer geometry and about other geologic factors that might 
affect fluid flow. Data the USGS collects will be used to improve 
three-dimensional, fluid-flow models to aid in the management of water 
resources.
    Because noise from seismic airguns and other acoustic instruments 
may result in the harassment or injury of marine mammals incidental to 
conducting the activity, an IHA under section 101(a)(5)(D) of the MMPA 
is warranted.
    Fieldwork described here will be the third airgun survey that the 
USGS has conducted under close supervision by marine-mammal biologists. 
In March 1998, the USGS used a large (6500 in3; 106 liters) 
airgun array in and around Puget Sound to study the regional earthquake 
hazard. The USGS employed 12 biologists, who worked on two ships 
continuously to oversee airgun operations. On several occasions, the 
USGS shut off the airguns when marine mammals entered safety zones that 
had been stipulated by NMFS under an IHA, and, when mammals left these 
zones, the USGS gradually ramped up the array as required to avoid 
harming wildlife. Marine mammal biologists reported that, during the 
survey, no overt distress was evident among the dense marine mammal 
populations, and, afterward, no unexplained marine mammal strandings 
occurred. In August 1998, the USGS surveyed offshore from Southern 
California, using a small airgun (40 in3; 655 
cm3). Marine mammal biologists oversaw this activity, and 
the survey the USGS proposes here will be conducted with similar 
oversight.

Experimental Design

    Marine studies conducted by the USGS focus on areas where natural 
hazards have their greatest potential impact on society. In Southern 
California, USGS studies will concern four areas. The first area in 
priority is the coastal zone and continental shelf between Los Angeles 
and San Diego, where much of the hazard appears to be associated with 
strike-slip faults, such as the Newport-Inglewood and Palos Verdes 
faults. The second study area lies offshore, in the Santa Monica, San 
Pedro, and San Diego Trough deeps, where rapid sedimentation has left a 
more complete record, relative to shallow-water areas, that the USGS 
can use to decipher earthquake history. The third area is the extension 
into the Santa Barbara Channel of major elements of onshore geology, 
including some large faults. The fourth area is the geologic boundary, 
marked generally by the Channel Islands, between the inner California 
Borderland (dominated by strike-slip faults) and the Santa Barbara 
Channel (dominated by compressional faults). The study proposed here 
focuses on the highest priority area, which lies near shore between Los 
Angeles and San Diego.
    The seismic-reflection survey will last 14 days. From its 
experience collecting seismic-reflection data in this general area 
during 1998, the USGS proposed to conduct the 1999 survey sometime 
within the May through July window. The basis for this decision is its 
desire to avoid the gray whale migrations and the peak arrival of other 
mysticete whales during late summer.
    The USGS has not yet determined the exact tracklines for the 
survey, but the USGS does know the areas where airgun use will be 
concentrated. Two of these areas are southwest and southeast of Los 
Angeles, and the third and largest one is west and northwest of San 
Diego. In these areas seismic-reflection data will be collected along a 
grid of lines that are about 2 km (1.2 mi) apart.
    The USGS proposes to use a small airgun and 200-m (656-ft) long 
streamer to collect seismic-reflection data. The potential effect on 
marine mammals is from the airgun; mammals cannot become entangled in 
the streamer. The USGS will also use a low-powered, high-resolution 
seismic system to obtain detailed information about the very shallow 
geology. The seismic- reflection system will be onboard a vessel owned 
by a private contractor. Ocean-bottom seismometers will be deployed to 
measure the velocity of sound in shallow rocks to help unravel the 
recent history of fault motion. These seismometers are passive 
recorders and pose no threat to the environment.
    Ship navigation will be accomplished using satellites of the Global 
Positioning System. The survey ship will be able to report accurate 
positions, which is important to mitigating the airgun's effect on 
marine mammals and to analyzing what impact, if any, airgun operations 
had on the environment.

[[Page 31550]]

The Seismic Sound Sources

    During this survey, the USGS will operate two sound sources--an 
airgun and a high-resolution Huntec(TM) system. The main 
sound source will be a single small airgun of special type called a 
generator-injector, or GI-gun (trademark of Seismic Systems, Inc., 
Houston, TX). This type of airgun consists of two small airguns within 
a single steel body. The two small airguns are fired sequentially, with 
the precise timing required to stifle the bubble oscillations that 
typify sound pulses from a single airgun of common type. These 
oscillations impede detailed analysis of fault and aquifer structure. 
For arrays consisting of many airguns, bubble oscillations are canceled 
by careful selection of airgun sizes. The GI-gun is a mini-array that 
is carefully adjusted to achieve the desired bubble cancellation. 
Airguns and GI-guns with similar chamber sizes have similar peak output 
pressures.
    The GI-gun for this survey has two equal-sized chambers of 35 
in3 (57 mm3), and the gun will be fired every 12 
seconds. Compressed air delivered to the GI-gun will have a pressure of 
about 3000 psi. The gun will be towed 12 meters (39.4 ft) behind the 
vessel and suspended from a float to maintain a depth of about 1 m (3.3 
ft).
    The manufacturer's literature indicates that a GI-gun of the size 
the USGS will use has a sound-pressure level (SPL) of about 220 dB re 1 
Pa-m. In comparison, a 40-in3 (65 mm3) 
airgun has an SPL of 216 dB re 1 Pa-m (Richardson et al., 
1995). The GI-gun's output sound pulse has a duration of about 10 ms. 
The amplitude spectrum of this pulse, as shown by the manufacturer's 
data, indicates that most of the sound energy is at frequencies below 
500 Hz. Field measurements by USGS personnel indicate that the GI-gun's 
emits low sound amplitudes at frequencies above 500 Hz. Thus, high-
amplitude sound from this source is at frequencies that are outside the 
main hearing band of odontocetes and pinnipeds (Richardson et al., 
1995).
    The high-resolution Huntec(TM) system uses an 
electrically powered sound source. In operation, the sound producing 
and recording hardware are towed behind the ship near the seabottom. 
The unit emits sound about every 0.5 seconds. This system provides 
highly detailed information about stratified sediment, so that dates 
obtained from fossils in sediment samples can be correlated with 
episodes of fault offset. The SPL for this unit is 210 dB re 1 
Pa-m. The output-sound bandwidth is 0.5 kHz to 8 kHz, with the 
main peak at 4.5 kHz.

Description of Habitat and Marine Mammals Affected by the Activity

    The Southern California Bight supports a diverse assemblage of 29 
species of cetaceans (whales, dolphins, and porpoises) and 6 species of 
pinnipeds (seals and sea lions). The species of marine mammals that are 
likely to be present in the seismic research area during the year 
include the bottlenose dolphin (Tursiops truncatus), common dolphin 
(Delphinus delphis), killer whale (Orcinus orca), Pacific white-sided 
dolphin (Lagenorhynchus obliquidens), northern right whale dolphin 
(Lissodelphis borealis), Risso's dolphin (Grampus griseus), pilot whale 
(Globicephala macrorhynchus), Dall's porpoise (Phocoenoides dalli), 
sperm whale (Physeter macrocephalus), humpback whale (Megaptera 
novaengliae), gray whale (Eschrichtius robustus), blue whale 
(Balaenoptera musculus), minke whale (Balaenoptera acutorostrata), fin 
whale (Balaenoptera physalus), harbor seal (Phoca vitulina), elephant 
seal (Mirounga angustirostris), northern sea lion (Eumetopias jubatus), 
and California sea lion (Zalophus californianus), northern fur seal 
(Callorhinus ursinus) and sea otters (Enhydra lutris). General 
information on these species can be found in the USGS application and 
in Barlow et al. (1997). Please refer to those documents for 
information on the biology, distribution, and abundance of these 
species.

Potential Effects of Seismic Surveys on Marine Mammals

General Discussion

     Seismic surveys are used to obtain data about rock formations up 
to several thousands of feet deep. These surveys are accomplished by 
transmitting sound waves into the earth, which are reflected off 
subsurface formations and recorded with detectors in the water column. 
A typical marine seismic source is an airgun array, which releases 
compressed air into the water creating an acoustical energy pulse that 
is directed downward toward the seabed. Hydrophones spaced along a 
streamer cable just below the surface of the water receive the 
reflected energy from the subsurface formations and transmit data to 
the seismic vessel. Onboard the vessel, the signals are amplified, 
digitized, and recorded on magnetic tape.
    Disturbance by seismic noise is the principal means of taking by 
this activity. Vessel noise may provide a secondary source. Also, the 
physical presence of vessel(s) could lead to some non-acoustic effects 
involving visual or other cues.
    Depending upon ambient conditions and the sensitivity of the 
receptor, underwater sounds produced by open-water seismic operations 
may be detectable some distance away from the activity. Any sound that 
is detectable is (at least in theory) capable of eliciting a 
disturbance reaction by a marine mammal or by masking a signal of 
comparable frequency. An incidental harassment take is presumed to 
occur when marine mammals in the vicinity of the seismic source (or 
vessel) react to the generated sounds or to visual cues.
    Seismic pulses are known to cause some species of whales, including 
gray whales, to behaviorally respond within a distance of several 
kilometers (Richardson et al., 1995). Although some limited masking of 
low-frequency sounds is a possibility for those species of whales using 
low frequencies for communication, the intermittent nature of seismic 
source pulses will limit the extent of masking. Bowhead whales, for 
example, are known to continue calling in the presence of seismic 
survey sounds, and their calls can be heard between seismic pulses 
(Richardson et al., 1986).
    When the received levels of noise exceed some behavioral reaction 
threshold, cetaceans will show disturbance reactions. The levels, 
frequencies, and types of noise that will elicit a response vary 
between and within species, individuals, locations and seasons. 
Behavioral changes may be subtle alterations in surface-dive-
respiration cycles. More conspicuous responses include changes in 
activity or aerial displays, movement away from the sound source, or 
complete avoidance of the area. The reaction threshold and degree of 
response are related to the activity of the animal at the time of the 
disturbance. Whales engaged in active behaviors, such as feeding, 
socializing, or mating, are less likely than resting animals to show 
overt behavioral reactions, unless the disturbance is directly 
threatening.
    Hearing damage is not expected to occur during the project. While 
it is not known whether a marine mammal very close to the airgun would 
be at risk of permanent hearing impairment, temporary threshold shift 
(TTS) is a theoretical possibility for animals very close to an airgun. 
However, planned monitoring and mitigation measures (described later in 
this document) are designed to detect marine mammals occurring near the 
seismic source(s) and to avoid, to the greatest extent practicable, 
exposing them to sound

[[Page 31551]]

pulses that have any possibility of causing hearing damage, including 
TTS.

Maximum Sound-Exposure Levels for Marine Mammals

    Loud continuous sounds can damage the hearing of marine mammals. 
However, the adverse effects of sound on mammals have been documented 
for exposure times that last for tens of seconds or minutes, but 
effects have not been documented for the brief pulses typical of the 
GI-gun (10 ms) and the Huntec(TM) system (0.3 ms). NMFS has 
long considered that the maximum SPLs to which marine mammals should be 
exposed from impulse sounds are 180 dB re 1 PaRMS 
for mysticetes and sperm whales, and 190 dB re 1 
PaRMS for odontocetes and pinnipeds. More recently, 
scientists at two workshops on acoustic noise and marine mammals 
supported NMFS' determination.
    At the time of its application, the USGS lacked detailed 
measurement of sound-transmission loss for the southern California 
offshore, so, based upon the best science available, the USGS estimated 
how SPL varies with distance from the airgun by assuming that sound 
decays according to 25Log(R). The coefficient 25 accounts approximately 
for the attenuation that is caused by the sound interacting with the 
seabottom. The USGS used this procedure to derive safety zone estimates 
based on the 220 dB SPL produced by the GI-gun, the larger of the two 
sound sources the USGS plans to use.
    Assuming that the 25Log(R) decay that the USGS used to estimate 
safe distances from the airgun is correct, this indicates that an SPL 
of 190 dB re 1 Pa is attained about 16 m (52.5 ft) away from 
the airgun, and an SPL of 180 dB re 1 Pa is attained at about 
40 m (131 ft) away. However, for precautionary reasons during field 
operations, the USGS proposes that, at all times, the safe distance for 
odontocetes and pinnipeds be 50 m (164 ft) and for mysticetes, 100 m 
(328 ft).

Comments and Responses

    A notice of receipt of the application and proposed authorization 
was published on March 5, 1999 (64 FR 10644), and a 30-day public 
comment period was provided on the application and proposed 
authorization. Comments were received from the Marine Mammal Commission 
(MMC), the California Coastal Commission (CCC), and one individual. The 
CCC asked a number of questions; those relevant to the application for 
an IHA are included here. Information on the authorization request and 
expected impact on marine mammal species, not subject to reviewer 
comments, can be found in the proposed authorization notice and is not 
repeated here, but is considered part of the record of decision, except 
as modified by this notice.
    On May 11, 1999, the CCC objected to the USGS project and its 
consistency determination, even though the CCC staff had recommended 
approval (see CD-32-99). During the May 11, 1999, public hearing, the 
USGS modified its project to avoid operating within the 3-mile limit of 
State waters and to expand the marine mammal safety radius for 
odontocetes to be the same as mysticetes (i.e., 100 m (328 ft) safety 
zone) in order to ensure that marine mammals would be exposed to no 
greater than 180 dB sound levels. Nevertheless, even with these 
modifications, the CCC found the project was not consistent to the 
maximum extent practicable with the California Coastal Management Plan 
(CCMP).
    The CCC further determined that alternative measures exist that 
would enable the project to be conducted in a manner consistent to the 
maximum extent practicable with the CCMP. One alternative measure 
identified by the CCC would require no night-time seismic activities. 
The CCC requirements are discussed later in this document. On May 28, 
1999, the USGS submitted a letter to NMFS, requesting the CCC suggested 
modifications be made to their application for an IHA.
     Comment 1: The MMC questions the statement in the USGS application 
that NMFS considers that the maximum sound pressure levels (SPLs) to 
which marine mammals can be exposed are 180 dB re 1 
PaRMS * * * for mysticetes and sperm whales, and 
190 dB re 1 PaRMS for odontocetes and pinnipeds. No 
citation was provided for this statement and, while the MMC is aware 
that the referenced sound levels were judged to be appropriate by the 
panel of experts convened by NMFS last September, the MMC was not aware 
that NMFS had accepted or made known the panel's findings in this 
regard. The MMC requests NMFS' rationale for these determinations.
     Response: NMFS notes that the mentioned SPLs have been adopted by 
NMFS as the lower bound for Level A harassment authorizations for 
impulse sounds, such as from seismic airguns (please refer to 50 CFR 
216.3 for a definition of Level A and Level B harassment), and have 
relatively long usage in establishing safety zones for marine mammals 
in such areas as the U.S. Beaufort Sea (see 61 FR 26501, May 28, 1996; 
61 FR 38715, July 25, 1996; 62 FR 38263, July 17, 1997; and 63 FR 
40505, July 29, 1998) and Puget Sound (see 62 FR 488817, September 17, 
1997, and 63 FR 2213, January 14, 1998). The rationale for using these 
levels was provided first in an authorization to the Exxon Corporation 
for seismic work in southern California in 1995 (see 60 FR 53753, 
October 17, 1995). Because of the length of that discussion, it is not 
repeated here. However, since the time of that authorization, NMFS has 
questioned the reliability of using data on humans as surrogates for 
marine mammal impacts. As a result, until better scientific data on 
marine mammals are collected, NMFS has adopted a more precautionary 
level of 190 dB as the lower bound for Level A harassment for 
odontocetes and pinnipeds, and not the higher levels noted in the Exxon 
authorization.
    NMFS wishes to clarify that, under section 101(a)(5)(D) of the 
MMPA, applicants may apply for a take by acoustic injury (Level A 
harassment); however, NMFS limits the use of authorizations for 
harassment involving the ``potential to injure'' to takings that may 
involve non-serious injury, such as TTS. Serious injury for marine 
mammals, such as permanent hearing loss within the species' primary 
hearing range, may lead fairly quickly to the animal's death. For 
example, if an application indicates that the short-term use of an 
acoustic source at its maximum output level has the potential to cause 
TTS in a marine mammal's hearing ability, that taking would constitute 
a Level A ``harassment'' take, since the animal's hearing ability would 
be expected to recover and, therefore, the section 101(a)(5)(D) 
application would be appropriate. However, if the acoustic source at 
its maximum level has the potential to cause a permanent threshold 
shift in a marine mammal's hearing ability or potentially could cause 
TTS over a significant period of time on the same animals, that 
activity will be considered by NMFS to be capable of causing serious 
injury to a marine mammal and, therefore, might not be appropriate for 
an IHA, unless effective mitigation was implemented to prevent more 
than non-serious injury.
    It should also be understood that, while NMFS considers that the 
maximum SPLs to which marine mammals should be exposed from impulse 
sounds are 180 dB re 1 PaRMS for mysticetes and 
sperm whales and 190 dB re 1 PaRMS for odontocetes 
and pinnipeds, the definition of ``harassment'' in section 3 of the 
MMPA authorizes takes by harassment to include injury (Level A 
harassment). As mentioned previously, 180 dB/190 dB SPLs are considered 
by NMFS to be the

[[Page 31552]]

lowest level of Level A harassment. This means that safety zones are 
established as a mitigation measure to reduce takings to the lowest 
level practicable as required by section 101(a)(5)(D)(ii)(I). 
Therefore, in accordance with section 101(a)(5)(D)(v), provided the 
applicant requested takes that included Level A harassment, the fact 
that a marine mammal entered the designated safety zone undetected is 
not considered a violation of the MMPA or of the IHA.
    In any case, in order to obtain a certificate of compliance 
(required of the USGS by the Coastal Zone Management Act) from the CCC, 
the USGS must observe the more restrictive 180-dB criterion for both 
mysticetes and odontocetes. Accordingly, the USGS, in a letter to NMFS, 
amended its application to indicate that a safety zone of 100 m (328 
ft) should be established, which is equivalent to 180 dB using 20Log(R) 
SPL.
     Comment 2: The CCC asked, if the operation includes shallow water, 
why 25Log(R) is an appropriate dispersion model? Also, one of the two 
sources, the Huntec system, emits sound at or near the bottom (if at 
all). Again, is the 25Log(R) the appropriate dispersion model for this 
source. If the assumption that 25Log(R) is the correct attenuation 
factor, the MMC recommends, in order to protect marine mammals from 
serious injury, that a more conservative estimate of the attenuation 
rate be used to calculate the safety zones, or that measurements be 
made at the beginning of the surveys to confirm the assumed 25Log(R) 
within the horizontal distances less than the depth of the water 
column.
     Response: The USGS notes that it used a 25Log(R) decay in SPL 
because acoustic modeling and measurements in the field show that sound 
decays quickly in water that overlies a sloping seabottom. In a medium 
with no acoustic interfaces, sound spreads spherically and SPL reduces 
at 20Log(R). A sloping bottom, however, causes sound to exit the water 
layer and beam into the underlying sediment, enhancing the transmission 
loss toward a beach (e.g., Jensen and Tindle, 1987; Deane and 
Buckingham, 1993; Glegg et al., 1993; Richardson et al., 1994; Jensen 
et al., 1994). In fact, a zone of high transmission loss, an ``acoustic 
shadow zone,'' lies just offshore from a beach. This argues against the 
common misunderstanding that underwater sound intensifies up-slope 
toward a beach.
    The enhanced transmission loss, relative to 20Log(R), that occurs 
over a sloping bottom has been verified by field measurements from 
scattered locations. The USGS, in conjunction with its 1997 seismic 
survey in Puget Sound (Fisher et al., 1999) measured sound decay with 
distance from a 108-liter (L) airgun array (Bain, 1999). A least-
squares, straight-line fit to data from ranges less than 10 km (5.4 nm) 
indicates that airgun sound decays at 29Log(R). In water 90 m (295 ft) 
deep off Los Angeles Harbor, USGS scientists measured a 26Log(R) 
transmission loss, using the same airgun the USGS will deploy this 
coming season. Off the Big Sur coast of central California, the SPL of 
a single 1.6 L airgun decreased at 25Log(R) decay toward the beach.
    Greenridge Sciences, Inc.(1998) measured the transmission loss of 
airgun sound at Platform Harmony in the Santa Barbara Channel. 
Estimated loss was high, the coefficient of the logarithm is 48 to 60. 
Finally, measurements of acoustic thermometry (ATOC) sounds versus 
distance, in nearshore water that is 10 m (33 ft) to 80 m (262 ft) 
deep, indicate a high transmission loss (TL) of about 43Log(R).
    Therefore, on the basis of abundant, numerical acoustic modeling 
and some field measurements, the USGS and NMFS believe that 25Log(R) is 
a conservative estimate of sound TL for airgun sounds over a sloping 
seabottom, like that offshore from southern California. In particular, 
sound that propagates into shallow water near and within the 3-mile 
(4.8 km) limit should decay sharply toward shore. However, the CCC will 
require the USGS to observe a 100-m (328-ft) safety radius around the 
airgun, which distance is consistent with the source level of the 
airgun and a 20Log(R) TL model. At this distance, received SPL would be 
180 dB using a 20Log(R) TL model. Because a more conservative estimate 
of the attenuation rate has been used to calculate the safety zones 
measurements, NMFS does not consider it necessary for measurements to 
be made at the beginning of the surveys to confirm the TL.
    The Huntec instrument is deployed at varying depths beneath the sea 
surface to avoid noise from large ships and ocean waves, but no attempt 
is made to maintain this instrument at a close distance to the sea 
floor. For safety reasons, the Huntec vehicle remains at least 50 m 
(164 ft) above the seafloor, except in water that is shallower than 100 
m (328 ft), where the Huntec will be at a depth of about 10 m (33 ft). 
The maximum deployment is 150 m (492 ft). The maximum SPL of the Huntec 
is about 25 percent of the G-I gun's maximum SPL, and mitigation zones 
were calculated to account for the GI-gun. These zones, therefore, are 
even more conservative for Huntec.
     Comment 3: The CCC asked how will marine mammals be observed and 
avoided during low-visibility times (such as night-time and fog)? Will 
there only be visual monitoring or is acoustic monitoring included as 
well.
     Response: The USGS proposes to rely on visual monitoring; there 
will not be any aerial surveys or acoustic monitoring. At night, 
biologists proposed to use light-amplification scopes to improve 
visibility and detection of the animals. However, in order for the USGS 
to be consistent to the greatest extent practicable with the CCMP, the 
USGS will not conduct GI-gun seismic surveys during nighttime.
     Comment 4: The MMC notes that marine mammal observers aboard the 
seismic vessels will need to work 6 hour shifts if seismic operations 
continue around the clock. The MMC questions whether two observers will 
be able to effectively monitor and detect marine mammals approaching 
the designated safety zones, particularly at night and after the first 
few days working the alternating 6-hour shifts. The MMC recommends that 
NMFS consult with the applicant to better determine the rationale for 
using two observers as proposed.
     Response: Three biological observers will be employed with two on 
watch at all times. According to restrictions placed on the USGS by the 
CCC, the USGS will be unable to use the airgun for 8 hours overnight, 
so all observers will benefit from a full, 8-hour sleep, and off-watch 
periods during the day offer additional rest.
     Comment 5: The CCC asks who will be conducting the marine mammal 
monitoring?
     Response: Employees of researchers at the Cascadia Research in 
Olympia, WA, will likely oversee monitoring.
     Comment 6: The CCC asks why a 35-in3 airgun is louder 
than a 45-in3 airgun? Is that because it contains two 
chambers?
     Response: The GI-gun uses 3000-psi pressure, while most airguns 
use 2000-psi pressure. This likely accounts for the greater source 
strength of the GI-gun.

Estimated Number of Potential Harassments of Marine Mammals

    The zone of influence for the GI-gun is defined to be the circle 
whose radius is the distance from the gun where the SPL reduces to 160 
dB re 1 Parms for those marine mammals that can 
hear either the low frequency sound from seismic airguns or the mid-
frequency Huntec system. For 25Log(R) TL, the zone of influence is 
estimated to be a

[[Page 31553]]

circle with a radius of 250 m (820 ft); for 20Log(R), the zone of 
influence would be 1,000 m. Based solely on estimated marine mammal 
populations within the survey area and on the number of individuals 
that were observed during the 1998 USGS survey and not on the expected 
number of animals that may be harassed by the GI-gun and Huntec system, 
the USGS estimates that up to 5 killer whales, 10 minke whales, 50 
northern sea lions, 100 northern fur seals, 100 northern elephant 
seals, 100 Dall's porpoise, 100 Risso's dolphins, 100 northern right-
whale dolphins, 100 Pacific white-sided dolphins, 100 bottlenosed 
dolphins, 200 California sea lions, 200 Pacific harbor seals, and 6,000 
common dolphins may be harassed incidental to the USGS survey. No 
mysticetes (except possibly minke whales) or sperm whales are expected 
to be in the area at the time of the survey and, therefore, would not 
be subject to incidental harassment, and no marine mammals will be 
seriously injured or killed as a result of the seismic survey. In 
addition, because the Huntec system will be towed near the seabottom 
and because the attenuation of mid-frequency sources is greater than 
low frequency sources, it is likely that few to no marine mammals at or 
near the surface will be affected by this acoustic instrument.

Mitigation of Potential Environmental Impact

    To avoid potential TTS injury to marine mammals, a safety zone will 
be established and monitored continuously by biologists, and the USGS 
must shut off the airguns whenever the ship and a marine mammal 
converge closer than 100 m (328 ft). However, because no authorization 
was requested to incidentally harass mysticetes (except minke whales) 
or sperm whales (since they're not expected to be in the area), a 
safety zone of 250 m (820 ft) will need to be monitored for these 
species.
    The USGS plans to have marine biologists aboard the ship who will 
have the authority to stop airgun operations when a mammal enters the 
safety zone.
    During seismic-reflection surveying, the ship's speed will be only 
4 to 5 knots, so that, when the airgun is being discharged, nearby 
marine mammals will have gradual warning of the vessel's approach and 
can move away. Finally, NMFS will coordinate with the local stranding 
network during the time of the survey to determine whether strandings 
can be related to the seismic operation.
    Additionally, in accordance with the May 28, 1999, request from the 
USGS, airgun activities will not be conducted during nighttime. This 
will decrease the potential that a marine mammal might enter the safety 
zone undetected.

Monitoring and Reporting

    Biologists, affiliated with the Cascadia Research Collective in 
Olympia, Washington, will monitor marine mammals at all times while the 
airguns are active. Three trained marine mammal observers will be 
aboard the seismic vessel to mitigate the potential environmental 
impact from airgun use and to gather data on the species, number, and 
reaction of marine mammals to the airgun. To ensure that no marine 
mammals are within the safety zone, monitoring will begin no later than 
30 minutes prior to the acoustic sources being turned on. Each observer 
will work shifts that limit on-watch times to no more than 4 
consecutive hours. Observers will use 7x50 binoculars with internal 
compasses and reticules to record the horizontal and vertical angle to 
sighted mammals. Monitoring data to be recorded during airgun 
operations include the observer on duty and weather conditions (such as 
Beaufort sea state, wind speed, cloud cover, swell height, 
precipitation, and visibility). For each mammal sighting, the observer 
will record the time, bearing and reticule readings, species, group 
size, and the animal's surface behavior and orientation. Observers will 
instruct geologists to shut off the airgun array whenever a marine 
mammal enters its respective safety zone.

Consultation

    Under section 7 of the Endangered Species Act, NMFS has completed 
consultation on the issuance of an IHA. NMFS finds this action to be 
unlikely to adversely affect listed marine mammals because the 
endangered whales are expected to be in offshore waters outside the 
Channel Islands at the time of the year that the activity will take 
place and northern sea lions, which are expected to be in more 
northerly waters during the summer, are not known to be affected by low 
frequency seismic sources unless close to the source.

Conclusions

    NMFS has determined that the short-term impact of conducting marine 
seismic-reflection data in offshore southern California may result, at 
worst, in a temporary modification in behavior by certain species of 
pinnipeds and cetaceans. While behavioral modifications may be made by 
certain species of marine mammals to avoid the resultant noise from the 
seismic airgun, this behavioral change is expected to have no more than 
a negligible impact on the animals.
    In addition, no take by serious injury or death is anticipated, and 
takes will be at the lowest level practicable due to the incorporation 
of the mitigation measures previously mentioned. No known rookeries, 
mating grounds, areas of concentrated feeding, or other areas of 
special significance for marine mammals occur within or near the 
planned area of operations during the season of operations.
    Since NMFS is assured that the taking would not result in more than 
the incidental harassment (as defined by the MMPA) of small numbers of 
certain species of marine mammals, would have only a negligible impact 
on these stocks, and would result in the least practicable impact on 
the stocks, NMFS has determined that the requirements of section 
101(a)(5)(D) of the MMPA have been met and the authorization can be 
issued.

Authorization

    Accordingly, NMFS has issued an IHA to the USGS for the possible 
harassment of small numbers of several species of marine mammals 
incidental to collecting marine seismic-reflection data offshore from 
southern California during the period from June 3 through July 31, 
provided the mitigation, monitoring and reporting requirements 
described in the authorization are undertaken.

    Dated: June 3, 1999.
Hilda Diaz-Soltero,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 99-14902 Filed 6-10-99; 8:45 am]
BILLING CODE 3510-22-F