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

[[Page 53753]]

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[I.D. 053095D]

Small Takes of Marine Mammals Incidental to Specified Activities;

Offshore Seismic Activities 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 to take small numbers of cetaceans by

harassment incidental to conducting a three-dimensional (3-D) seismic

survey in the Santa Ynez Unit (SYU), located in the western portion of

the Santa Barbara Channel, offshore California, in Federal waters has

been issued to the Exxon Company, U.S.A., Thousand Oaks, CA, for a

period of approximately 2 months.

EFFECTIVE DATE: This authorization is effective from October 11, 1995

through December 31, 1995.

ADDRESSES: The application, authorization, programmatic environmental

assessment (EA), and reference lists are available from the following

offices: Marine Mammal Division, Office of Protected Resources, NMFS,

1315 East-West Highway, Silver Spring, MD 20910 and the Southwest

Region, NMFS, 501 West Ocean Blvd. Long Beach, CA 90802.

A copy of the EA for the 3-D seismic survey in the SYU is available

from the Minerals Management Service (MMS), Pacific Region, 770 Paseo

Camarillo, Camarillo, CA 93010.

FOR FURTHER INFORMATION CONTACT: Kenneth Hollingshead, Office of

Protected Resources at 301-713-2055, or Irma Lagomarsino, Southwest

Regional Office at 310-980-4016.

SUPPLEMENTARY INFORMATION:

Background

Section 101(a)(5)(A) 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 regulations are

issued.

Permission may be granted if NMFS finds that the taking will have a

negligible impact on the species or stock(s); will not have an

unmitigable adverse impact on the availability of the species or

stock(s) for subsistence uses; and the permissible methods of taking

and requirements pertaining to the monitoring and reporting of such

taking are set forth.

On April 30, 1994, the President signed Public Law 103-238, The

MMPA Amendments of 1994. One part of this law added a new subsection

101(a)(5)(D) to the MMPA to establish 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 for a

period of up to 1 year. The MMPA 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.

New 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.

On May 11, 1995, NMFS received an application from Exxon requesting

an authorization for the harassment of small numbers of certain species

of cetaceans incidental to conducting a 3-D seismic survey within the

SYU, located in the western portion of the Santa Barbara Channel, off

Southern California, in U.S. waters. The species requested are as

follows: Blue whale (Balaenoptera musculus), fin whale (Balaenoptera

physalus), sei whale (Balaenoptera borealis), humpback whale (Megaptera

novaeangliae), minke whale (Balaenoptera acutorostrata), Bryde's whale

(Balaenoptera edeni), gray whale (Eschrichtius robustus), sperm whale

(Physeter macrocephalus) and pygmy sperm whale (Kogia breviceps).

Exxon's survey will cover an area of approximately 117 mi2

(303 km2) of the outer continental shelf and will require

approximately 45-60 days, commencing in late October 1995, to complete.

The survey will provide subsurface data that will enable Exxon to more

accurately assess the oil and gas reservoirs in order to optimally

locate future development wells from existing platforms.

In addition to a press release, notices were published in

newspapers of general circulation in Santa Barbara and Ventura

Counties, the areas adjacent to the SYU survey area. Also a notice of

receipt of Exxon's application and the proposed authorization were

published in the Federal Register (June 7, 1995, 60 FR 30066) and a 30-

day public comment period was provided on the application and proposed

authorization. The comment period closed on July 7, 1995. During the

comment period, 9 letters were received. Beginning September 13, 1995,

more than 2 months after the comment period closed, NMFS received

several additional comments. NMFS is under no obligation to accept

comments received after close of the comment period. Nevertheless, NMFS

considered the concerns raised by the late comments, and because NMFS

believed that valid points had been made, took them into consideration

in finalizing the incidental harassment authorization. Comments

relative to Exxon's incidental harassment authorization request are

discussed below. Other than information necessary to respond to the

comments, additional background information on the activity and request

can be found in the above-mentioned documents and does not need to be

repeated here.

Comments and Responses

Activity Concerns

Comment 1. One commenter had concerns that neither the application

nor the proposed authorization addressed the operation of the 3-D

seismic array in sufficient detail, thereby preventing a detailed

analysis of the impacts. This same commenter questioned the duty cycle

and that signals with quick rise and fall times do not allow the animal

time to auditorially accommodate the noise.

Response. The commenter is correct that there was absent from the

discussion any mention of the peak source level for the seismic array.

However, like the commenter, NMFS used data provided in Richardson et

al. (1991)1 and Malme et al. (1984). These references indicate

that a seismic array would have a sound pressure level (SPL) of between

226 dB and 239 dB (re 1 Pa) at 1 meter (m) from the source.

Information not available at the time of receipt of the application

indicates that air gun arrays may produce broadband peak source levels

as high as 240-250 dB (re 1 Pa), but that much of this total

output is directed downward; horizontal

[[Page 53754]]

propagation is 230-235 dB (MMS, 1995). Air gun pulse components are

strongest around 50-100 Hz, although there is considerable energy in

the 20-250 Hz range (Richardson and Malme, 1993 as cited in MMS, 1995).

Exxon's contractor for the surveys, who had not been selected at the

time of the proposed authorization's publication, has indicated that

his seismic arrays will have a maximum output of 215 dB at a distance

of 8 m and will result in fewer west-east transects (55 v 64) than

estimated in the application and proposed authorization. This array

will therefore result in lower sound pressure levels at a given

distance from the source than was predicted in the proposal.

\1\A list of references used in this document can be obtained by

writing to the address provided above (see ADDRESSES).

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While the proposed authorization noted that the 195 dB isopleth

would be located approximately 300 ft (91.5 m) from the source,

recalculations (based upon the 20LogR transmission loss model),

indicate that 195 dB will occur at 246 ft (75 m) from the source. This

is the area within which NMFS was originally concerned that temporary

or permanent threshold-shift (TTS/PTS) injury potentially could take

place (if the animal remained in this relatively small area for any

length of time and had the ability to hear in the frequencies of the

source) and therefore, in order to protect all species of marine

mammals from potential auditory injury, the seismic array must be

turned off whenever any marine mammals are sighted within the area and/

or must not be powered up whenever marine mammals are within the area.

NMFS recognizes that some marine mammals are deep divers and may not be

visible on the surface, and that night-time operations will limit

observations outside the safety zone. NMFS is confident however, that

no marine mammals will remain within this area because (1) The vessel

is underway at a speed of approximately 5 knots (9.26 km/hr), less than

the normal swimming speed of marine mammals, allowing them sufficient

advance notice of the seismic array (if they hear the noise) and, if it

disturbs them, to move away from the source; (2) it is presumed that

water turbulence from the vessel, the paravanes and streamer array will

tend to deter marine mammals from approaching the source even if they

do not hear the source; and (3) the requirement to ramp-up whenever the

source is turned on.

The seismic source will consist of dual air gun arrays deployed

approximately 120 ft (37.5 m) apart and fired alternately to acquire

separate records. Each array will consist of 18 guns of different

strengths. Each array will transmit every 8 to 9 seconds (depending

upon vessel speed), while the vessel is on a trackline, creating a

regular series of strong noise impulses, with short pulses separated by

silent periods lasting 5-15 seconds, depending on survey type and depth

of target strata. While the science is unclear on the relationship

between the duty cycle of a seismic source and the potential for

auditory damage to a marine mammal, because of the slow vessel speed,

and the requirements to both terminate the source whenever marine

mammals are within the safety zone and to employ ramp-up, NMFS believes

that the likelihood that a marine mammal would voluntarily remain in

close proximity to the source in the presence of pain or annoyance, and

thereby be seriously injured by the towed acoustic array, is remote.

Marine Mammal Species Impacts

Comment 2. Three commenters were concerned that seismic surveys

disturbed other marine mammal species in addition to the large whales,

especially the harbor seal and the California sea lion. Also, comments

were received after the close of the comment period that (1) Seismic

arrays produced seismic noise in frequencies up to 1 kHz at levels

sufficient to harass odontocetes and pinnipeds and (2) that the correct

transmission loss model for the seismic area was not 20LogR but more

likely 15 or 17LogR which would affect both designated safety zones and

the number of marine mammals affected. Based upon measurements made in

the Beaufort Sea in 1993, one commenter believed that a 160 dB isopleth

should extend 27.4 km, not 5.2 km as proposed.

Response. NMFS would like to clarify for reviewers that being able

to hear certain sounds (noise) does not necessarily mean that a marine

mammal is being physiologically stressed (harassed) by that sound. In

addition, when noise is frequent, marine mammals may habituate to it

once the determination is made that injury or harm does not result.

In order to be detectable by a marine mammal, noise needs to be

greater than ambient within the same frequency band as the animal's

hearing range. The further outside the species' principal (best)

hearing range the noise occurs, the greater (louder) sounds need to be

in order to be detectable, bothersome, or injurious.

Seismic airgun arrays emit pulsed energy at frequencies in the 20

to 250 Hz range, with a peak SPL usually between 226 dB and 239 dB (re

1 Pa) at 1 m. Exxon calculated (and the manufacturer has

confirmed) that its seismic array would have an SPL of 215 dB at a

distance of 8 m from the geometric center of the source (or

approximately 1 m from the outside of the array) and based its

transmission loss calculations using the 20LogR model, even though

Malme et al. (1986) indicated that for offshore California seismic

work, a less conservative, 25LogR model was appropriate. The 8 m/20LogR

model indicated SPLs would attenuate to approximately 195 dB at 246 ft

(75 m), 190 dB at 451 ft (137.5 m), 180 db at 1,476 ft (450 m) and 160

dB at 2.84 nautical miles (nm) (5.2 km). Based upon comments that the

20LogR transmission loss model was not appropriate for coastal

California waters, Exxon has again recalculated transmission loss

estimates based upon an industry standard of 1 m from geometric center

of the source. This model indicates that SPLs would attenuate

approximately as follows:

Distance From Source (ft/m)

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Sound level 20LogR 17LogR 15LogR

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195 dB...................... 32.9/10................... 49.2/15................... 72.1/22

190 dB...................... 58.4/17.8................. 96.8/29.5................. 152.4/46.5

180 db...................... 187.0/57.................. 377.3/115................. 705.4/215

170 dB...................... 587.3/179................. 1492.8/455................ 3280.8/1000

160 dB...................... 1837.2/560................ 5643.0/1,720.............. 15419.8/4700

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As these distances are significantly less than the distances proposed

earlier for 8m/20LogR, NMFS has determined that the more cautious

approach, using 8 m/20LogR model, should be used for this

authorization. The commenter who

[[Page 53755]]

suggested that 1993 Beaufort Sea survey data should be used

acknowledged that his model may not be ``completely accurate for the

Santa Barbara Channel,'' but believed it was appropriate for planning

purposes. NMFS is unaware of the parameters involved with the Beaufort

Sea measurements (e.g., water temperature, depth, bottom topography,

ice cover), but in general those characteristics are quite different

from those off Southern California.

In the proposed authorization, NMFS stated that dolphin, porpoise,

seal, and sea lion hearing is believed to be poor at frequencies less

than 1,000 Hz, and thus it is unlikely that the airgun noise would

significantly affect them. One commenter correctly pointed out that

``significantly affect a marine mammal'' is not the appropriate

criterion, and that the appropriate criterion is that the activity have

a negligible impact. This commenter recommended NMFS provide a more

thorough rationale for the determination that species other than large

whales will not be taken by harassment incidental to the seismic

surveys and that the takings of large whales will be limited to

harassment.

Within the pinniped suborder, Schusterman et al. (1967) have

determined that none of the species tested to date have exhibited good

hearing capabilities at low frequencies, although the northern elephant

seal, California sea lion, and harbor seal appear to have some

communication ability within the upper low-frequency band (100-1,000

Hz). Underwater audiograms indicate that pinnipeds and odontocetes are

particularly sensitive to sound with frequencies in the 2-12 kHz range

(Richardson et al., 1991). Seals and sea lions have thresholds of

roughly 60 to 80 dB (re 1 Pa) in the range of best hearing.

Phocid seals have lower thresholds and a wider frequency range of

hearing than otariid seals. Pinniped hearing in sub-1 kHz range varies

from 85 dB at 1 kHz to 114 dB at 250 Hz for the California sea lion,

70-85 dB at 1 kHz for the harbor seal, and 95 dB at 1 kHz for the

northern fur seal (Richardson et al., 1991). No information has been

reported concerning the in-water hearing of northern elephant seals

(Richardson et al., 1991), although Schusterman (as cited in Advanced

Research Projects Office, 1995) believes they may have mid- to low-

frequency hearing ability.

No studies have focused on pinniped reaction to underwater noise

from pulsed, seismic arrays in open water (Richardson et al., 1991), as

opposed to in-air exposure to continuous noise. However, assuming an

SPL needed to be 80-100 dB over its threshold in order to cause

annoyance and 130 dB for injury (pain), as is the current thought based

upon human studies (ARPA, 1995), it appears unlikely that pinnipeds

would be harassed or injured by low frequency sounds from a seismic

source unless they were within close proximity of the array (114

dB2 + 80 dB = 190 dB (harassment); 114 dB2 + 130 dB = 244 dB

(injury)). At the upper end of the seismic array's frequency (1 kHz),

sufficient energy to cause harassment would occur at a distance of only

1-3 m from the source while TTS injury takes would not occur (70 dB

(harbor seal) - 85 dB (California sea lion) + 80 dB = 150-165 dB

(harassment); 70 dB (harbor seal) - 85 dB (California sea lion) + 130

dB = 200-215 dB (injury)).

\2\Extrapolated from Figure 7.2 in Richardson et al. (1991).

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For permanent injury, marine mammals would need to remain in the

high noise field for extended periods of time. Existing evidence also

suggests that, while they may be capable of hearing sounds from seismic

arrays, seals and sea lions appear to tolerate intense pulsatile

sounds, without known effect, once they learn that there is no danger

associated with the noise (see for example, NMFS/WDFW, 1995). In

addition, they will apparently not abandon feeding or breeding areas

due to exposure to these noise sources (Richardson et al., 1991) and

may habituate to certain noises over time. Since seismic work is common

in southern California waters, pinnipeds have previously been exposed

to seismic noise, and may not react to it. However, because the

evidence indicates that pinnipeds could be incidentally harassed at an

SPL of 190 dB or greater, and because Exxon has not requested an

incidental harassment authorization for pinnipeds, NMFS will require,

as part of the authorization, that a safety zone around the source be

established at the 190 dB isopleth or 451 ft (137.5 m) from the source.

For added protection, this zone will include the entire area from the

stern of the vessel out to the paravanes or approximately 500 ft (152.4

m) from the source.

For odontocetes, based upon the best scientific evidence available,

NMFS concludes that the hearing of dolphins, porpoises and other small

whales that inhabit the Channel Islands area is poor at frequencies

less than 1,000 Hz, and thus it is unlikely that the airgun noise would

affect them. While odontocetes can hear sounds over a very wide range

of frequencies, from as low as 75-125 Hz in bottlenose dolphins and

belugas (Johnson, 1967; Awbrey et al., 1988) to 105-150 kHz in several

other species (Richardson et al., 1991), underwater audiograms indicate

that odontocetes hear best at frequencies above 10 kHz. However, none

of the seismic source frequencies will be within the dominant

frequencies used by odontocetes for vocalization (Richardson et al.,

1991).

In the range of best hearing (10 kHz-90 kHz), odontocetes have

thresholds in the range of 40 to 60 dB re 1 Pa. In the absence

of noise, bottlenose dolphins can detect a signal of about 41-42 dB at

various frequencies between 10 kHz and 100 kHz (Johnson, 1967, 1968).

For frequencies from 100 Hz to roughly 1000 Hz however, hearing

thresholds range from 130 dB to 90 dB re 1 Pa, suggesting the

potential for an increased tolerance for low frequency sound. Other

odontocete species appear to have similar threshold frequencies (see

Richardson et al., 1991). If one accepts one commenter's premise and

Richardson et al.'s (1991) conclusion, that, based upon studies on

humans, SPLs of 80-100 dB over threshold are necessary in order to

cause annoyance and 130 dB for injury (pain) in odontocetes, most

odontocetes would probably need to be almost adjacent to the seismic

source, and intentionally remain there, in order to be affected by the

seismic array (110 dB3 + 80 dB (harassment) = 190 dB; 110 dB + 130

dB (injury) = 240 dB). At the upper end of the seismic array's

frequency (1 kHz), sufficient energy would not occur that would cause

either harassment or TTS injury takes to occur (90 dB + 80 dB = 170 dB

(harassment); 90 dB + 130 dB = 220 dB (injury)).

\3\ Extrapolated from Figure 7.1 in Richardson et al. (1991).

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However, NMFS cautions that testing on the similarity between

hearing capabilities between humans and marine mammals still needs to

be conducted before more than hypothetical conclusions can be drawn.

Similar to pinnipeds, because the evidence indicates that odontocetes

(other than the sperm whale) could be incidentally harassed at an SPL

of 190 dB or greater, and because Exxon has not requested an incidental

harassment authorization for odontocetes (other than the sperm whale),

NMFS will require, as part of the authorization, that a safety zone

around the source be established at the 190 dB isopleth or 451 ft

(137.5 m) from the source. For added protection, this zone will include

the entire area from the stern of the vessel out to the paravanes, or

approximately 500 ft (152.4 m) from the source.

Therefore, whether or not the above mentioned marine mammal species

can hear seismic array sounds, their

[[Page 53756]]

estimated area of potential harassment and/or auditory damage remains

entirely within the area bounded by the vessel, the paravanes and the

streamer cables. As Exxon will be required to turn off the array if any

species of marine mammal is sighted within this new 500-ft (152.4 m)

safety zone, to ramp-up the array slowly (see below), and, if any

marine mammals are observed within the 500-ft (152.4-m) safety zone,

delay operations until all marine mammals are outside the zone, it is

unlikely that pinnipeds or odontocete cetaceans (except sperm whales)

will be incidentally harassed by the seismic array and therefore, an

authorization is not needed for these species. It can also be presumed

that any marine mammals that consistently remain in the vicinity of, or

swim along with, the vessel or its equipment, are not being harassed by

the vessel or the array.

For mysticete and sperm whales, NMFS has reviewed the evidence and

has determined that, because an authorization for serious injury has

not been requested for these species, a no-injury safety zone should be

established that, based upon the best evidence, would preclude injury.

NMFS has determined that injury may occur at a level of 180 dB or

greater and has therefore established, through the authorization, a

safety zone for these species at a distance of 1,476 ft (450 m) from

the source. While there are indications, based upon the Heard Island

assessment, that injury may occur at the 160 dB SPL, because the 160 dB

SPL is where Malme et al. (1984) noted 10 percent avoidance behavior

for gray whales, and injury appears to be about 30 dB higher than the

onset of harassment, 160 dB may be an overly conservative level for

injury takes. However, because mysticete sensitivity is likely greater

than that of odontocetes, 190 dB appears too high for these species.

Therefore, a safety zone established at the 180 dB level appears

warranted.

Comment 3. Several commenters noted that Exxon's survey period was

for 60 days but that NMFS' proposed authorization was for a period of 1

year. These commenters recommended either that the period of time not

extend past the period when the gray whale migration begins, because

the analyses have not been conducted to assess the risk of adversely

affecting this migration or that the authorization period end at the

same time (December 31st) that the California Air Pollution Control

District's (APCD) permit for the survey. One of these commenters also

questioned the calculated level of take of gray whales (and other

species), noting that, for gray whales, the level depended upon the

timing of the survey and, therefore, might be greater than proposed.

For other species, the commenter was concerned that the proposed

authorization used average densities along the coast of California and

may seriously over- or under-estimate abundance.

Response. While one commenter is correct that NMFS originally

proposed to issue a 1-year authorization, NMFS has accepted the other

commenter's suggestion and will limit the authorization to a period of

validity of the APCD permit (December 31, 1995).

In its proposed authorization, NMFS assumed that gray whales could

be incidentally harassed if the survey extended into the gray whale

migratory period (southbound--mid-December through early February;

northbound--mid-February through May) and therefore, included that

species under the proposed incidental harassment authorization. Because

Barlow (1995) did not observe any gray whales during his summer/fall

ship surveys, incidental harassment levels were based upon fall/winter

gray whale density calculations found in Forney et al. (1995).

It should be noted that for incidental harassment takings, NMFS

does not consider its calculations to be quotas, but only a guide for

making the MMPA negligible impact determinations. The two tables in the

proposed authorization indicate that, based upon density calculations

in Forney et al. (1995), NMFS estimated that, if the survey extended

into the latter part of December, on average, 11 gray whales could be

within the area at any one time. Because of the method of operation of

the seismic array (as explained in the proposed authorization), NMFS

has calculated that there could be 341 incidental harassment takings of

gray whales, but that this level could increase or decrease somewhat

depending upon the time of the year, pod size, and the actual location

of the seismic vessel (onshore/offshore). This number may vary also due

to the time of the survey in relation to gray whale migration, if the

survey ends early, the number of harassments would be lower than it the

survey continued into the peak migration period in late January.

However, whether the estimate is an under- or over-estimate, with a

migration rate of approximately 3-4 mi/hr (5.5-7.7 km/hr), an

individual gray whale would be expected to be harassed only during a

single-line transect by the vessel and the length of time the animal is

exposed to the noise would depend upon its direction and distance in

relation to the seismic vessel's direction and speed and any action the

animal might take to avoid the noise. Therefore, although the potential

exists that the seismic array noise could result in gray whale

harassments, and although Exxon will make every effort to complete the

survey prior to the start of the gray whale period, an authorization

remains necessary for this species because of the possibility of survey

delays.

During their southbound migration, gray whales migrate near shore

along the coast of North America from Alaska to central California. In

1993 and 1994, 95.6 percent and 98.7 percent of the southbound gray

whales passed within 3 nm (5.6 km) of the Granite Canyon area of

central CA (Withrow et al., 1995). After passing Point Conception,

California, Rice et al. (1984) believed the majority of the animals

took a more direct offshore route across the southern California Bight

to northern Baja California. This route passes Santa Rosa and San

Nicolas islands, the Tanner and Cortes banks and into Mexican waters

(MMS, 1992), well away from Exxon's seismic survey area. Other routes

include the nearshore route which follows the mainland coast of

California, and the inshore route which passes through the northern

Channel Island chain to Santa Catalina or San Clemente Island and on

into Mexico. Although seismic array noise may be detectable to those

gray whales using the offshore and inshore routes, the noise levels at

those distances are not expected to result in any behavioral

modification or require animals to deviate from their planned migratory

path. Therefore, it is anticipated that only those gray whales on the

nearshore route would come into the vicinity of the seismic array and

potentially be disturbed by it.

Assuming that nearshore migratory animals would be within 3 nm (5.6

km) (Withrow et al., 1995) of the coastline as in central California,

this portion of the population could potentially be subject to

disturbance by seismic noise if the survey continued into the migratory

period. However, even though NMFS believes that few gray whales will be

migrating through the area prior to the time the authorization expires

on December 31, 1995, and therefore any harassment takings that do

occur would have only a negligible impact on the eastern Pacific stock,

in order to ensure that those early migratory gray whales have an

unimpeded migratory corridor, NMFS will require, as part of the

authorization, that an NMFS biologist be on board the seismic and/or

another auxiliary support vessel to monitor gray whale behavior. This

individual would

[[Page 53757]]

have authority, under the authorization, and with the concurrence of

the Regional Director, to modify or terminate the authorization if this

individual determines that gray whales are not able to migrate through

the SYU area.

Comment 4. One commenter was concerned about other potential causes

of incidental harassment or other forms of taking by, for example,

entanglement in streamer cables, vessel noise, or support vessels and

aircraft. Another commenter believed that disturbance by whale watch

vessels circling the animals was more likely than disturbance by a

seismic array.

Response. All vessels create underwater noise that is potentially

detectable by marine mammals and, based upon distance between the

mammal and the source, may have the potential to cause disturbance to

the animal. If owners or operators of these vessels (other than

commercial fishing vessels) believe that their vessels may be harassing

marine mammals, they should apply for incidental harassment

authorizations. However, the operation of one or two seismic and

support vessels or aircraft for a 45- to 60-day period is expected to

have a negligible impact on marine mammals. Vessel noise is likely to

be indistinguishable from the noise caused by the approximately 19,800

round trips annually by vessels, other than commercial-fishing boats,

into Los Angeles/Long Beach (LA/LB) harbor. It should be noted that the

southwestern portion of the survey area is adjacent to the LA/LB

shipping lanes and, therefore, is already subject to anthropogenic

noise. To avoid additional harassment authorizations, except in

emergency situations, aircraft supplying the seismic vessels are

requested to maintain an altitude of 1,000 ft (305 m) until within

3,038 ft (.5 nm; 926 m) of the seismic vessel, unless conducting

surveys for marine mammals.

The streamer array, along which the passive hydrophones are

located, will consist of 6 cables in parallel. The individual cables

will be 9,840 ft (3,000 m) long and spaced 246 ft (75 m) apart,

typically towed at a depth of 16.4 to 32.8 ft (5 to 10 m) below the

water surface. Hydrophones are attached along the cable and paravanes

will be deployed to separate the streamer arrays. The cables have a

diameter of 3.5-4 inches (8.9 to 10.2 cm); therefore, it is very

unlikely that a marine mammal would become entangled in one. More

likely, the presence of the vessel and the water turbulence from the

paravane and streamer cables will provide a zone around the source that

marine mammals will not enter. In addition, because of the slow ship

speed and resultant water turbulence and noise, it is extremely

unlikely that any marine mammals would be struck and thereby injured or

killed by the seismic vessel.

Mitigation and Monitoring Concerns

Comment 5. Two commenters were concerned that the criterion for the

Acoustic Thermography of Ocean Climate (ATOC) project having a

potential to cause harassment has been established at 120 dB, while the

3-D seismic survey's zone of influence (ZOI) was proposed for 160 dB.

Another commenter questioned whether some marine mammals would hear the

seismic pulse outside the 160 dB isopleth since Tyack (1988) indicated

that 10 percent of the gray whales showed behavioral changes at that

range.

Response. It is presumed that certain species of marine mammals

outside the 160 dB isopleth will hear the seismic array. For California

waters, Richardson et al. (1991) estimated that airgun sound pulses

would remain above typical ambient noise levels (approximately 75-90

dB) at distances greater than 60 mi (100 km) from the source. However,

as stated previously, being able to hear certain frequency sounds does

not necessarily mean that the marine mammal is being physiologically

stressed by that sound.

Based upon Tyack (1988), who indicates that avoidance behavior

occurs only at relatively close ranges at decibels greater than 120 dB

for continuous noise and 160-170 dB for pulsed sounds such as from

airguns, the marine mammal ZOI for seismic work is considered to be the

160 dB isopleth because seismic arrays are pulsed noise generators

whereas activities such as ATOC result in continuous sound and

therefore has a ZOI set at the 120 dB isopleth. For pulsed sounds such

as airgun arrays, Tyack found that fewer than 10 percent of the animals

located beyond the 160 dB range would show avoidance behavior to the

noise. However, because noise level measurements are logarithmic,

extending the potential ZOI to the 150 dB isopleth, as one commenter

suggests, may unnecessarily impose a larger ZOI. For reference

purposes, it should be noted that ZOI and the terms ``zone of potential

disturbance'' and ``zone of potential harassment'' used in the proposed

authorization, are all considered synonymous.

Comment 6. Two commenters expressed opposing concerns regarding

NMFS' proposed mitigation measure that would require Exxon to leave the

array on if restarting the array would occur during nighttime hours. A

third commenter noted that NMFS' proposed authorization and the Exxon

application differed in that the applicant appeared to envision

monitoring occurring day and night while NMFS envisioned it to occur

only during the day.

Response. One of the mitigation measures proposed by NMFS was for

the airgun arrays to be shut down during turning and maneuvering, and

then be powered up slowly over a 5-minute period. NMFS also proposed

that whenever the array was turned off during nighttime that the array

not be repowered until daylight. As a result of comments, difficulties

with this proposed mitigation measure were identified. If the survey

vessel is not authorized to power up the array during nighttime, the

duration of the survey could be doubled, resulting in increased total

air emissions, fishing preclusion time in the survey area, and costs to

the applicant, although the number of marine mammal incidental

harassments would probably not increase or decrease substantially. In

addition, NMFS has been informed that crew safety concerns will prevent

leaving an array powered up whenever work is needed on the rear deck.

Unfortunately, while leaving at least partial power to one of the

arrays at times when repairs are underway should alert marine mammals

to the presence of the array and prevent potential auditory damage,

this could also result in additional harassments. It is NMFS' view that

ramping up the acoustic array and use of lights to illuminate most of

the 500 ft (152.4 m) safety zone, no serious injury of a marine mammal

should result during nighttime operations. Therefore, NMFS will not

require a mitigation requirement prohibiting turning on an array in

darkness but will modify ramp-up to require the array be linearly

increased by no more than 6 dB/min above 160 dB. This will increase the

ramp-up period from 5 minutes to approximately 15 minutes and will

further ensure that marine mammals can vacate the immediate survey area

if they so choose, prior to potential onset of a temporary threshold

shift injury or less serious harassment.

Comment 7. Two commenters recommended a greater distance between

the vessel and cetaceans prior to turning on and ramping up of the

seismic array. One commenter recommended that the seismic array not be

turned on if marine mammals were within the 160 dB isopleth while the

other commenter noted that within state

[[Page 53758]]

waters mitigation measures prohibit the array from being powered up

whenever cetaceans are within 1.2 nm (2 km) of the survey boat.

Response. While NMFS has established a safety zone for pinnipeds

and odontocetes at 500 ft (152.4 m) and increased the safety zone for

mysticetes to 1,476 ft (450 m), there are several difficulties with

requiring that the seismic device not be turned on if marine mammals

are visible within the 160 dB isopleth. The 160 dB isopleth occurs at a

radius of approximately 2.84 nm (5.2 km) from the seismic source and,

based upon estimates made by NMFS in the proposed authorization,

mysticete/sperm whale harassment incidents are predicted to occur

within this zone. Because harassment takings of mysticetes are

authorized, and harassment takings of odontocetes and pinnipeds are not

expected to occur unless the animals were within the 190 dB isopleth,

termination of the seismic source, if marine mammals are seen within

the 160 dB isopleth, is not warranted. In addition, if Exxon were

required to cease operations each time one of these animals was

sighted, or whenever a pinniped and odontocete was sighted (which

evidence indicates will not be disturbed by seismic array noise in this

area), the survey would result in many data gaps. Depending upon the

frequency of shutting off the array and powering it back up, track

lines could have serious data gaps requiring all or portions of the

track-line to be resurveyed. This would result in increased survey

time.

Because harassment takings only are being authorized by this

action, and because implementing this recommendation is not likely to

result in a lesser impact on marine mammals in the long-term, NMFS does

not believe that it is necessary to require this mitigation measure.

A distance of 1.2 nm (2 km) from the survey vessel, while less

conservative than a 2.84 nm (5.2 km) safety zone, may be unwarranted

and impractical for the same reasons.

In addition, some cetaceans have been reported approaching seismic

survey vessels. If true, this would be evidence that certain species of

marine mammals either do not hear the array or the noise is not

disturbing the animal. NMFS believes that to require this mitigation

measure would impose an unnecessary burden on Exxon, since it would be

required to wait until all marine mammals voluntarily move away from

the area before resuming the survey. Observers however, will be

required to record all marine mammal behavior patterns within the 2.84

nm (5.2 km) ZOI. One purpose of these observations will be to determine

whether pinnipeds and odontocetes react to seismic noise. This

information will then be available for consideration in future seismic

applications.

Comment 8. One commenter recommended that NMFS require Exxon to

implement monitoring methods similar to that used by seismic and oil

development activities in the Beaufort Sea, including an extensive

aerial monitoring program.

Response. While a monitoring protocol based upon monitoring

guidelines recommended for use in the Beaufort Sea will be provided to

Exxon, aerial monitoring is an expensive undertaking whose benefit for

marine mammals must be weighed against the cost of undertaking the

program. In the Beaufort Sea, an extensive monitoring program has been

implemented by MMS since 1979 and MMS and NMFS since 1986, particularly

since 1991, to determine among other things, whether oil and gas

exploration and development activities were having a more than

negligible impact on the availability of bowhead whales for subsistence

purposes during the fall migration of bowheads. More extensive

monitoring requirements were recommended because extensive activities

were conducted (i.e., seismic work, actual drilling, icebreaking

operations and supply ship and aircraft activities) and there were

concerns that such activities might drive bowheads so far offshore that

they would become unavailable for subsistence purposes. Secondary use

of the monitoring program was to determine the level of harassment

takings to bowheads and several other marine mammal species. Aerial

monitoring was augmented by vessel observations, but other mitigation,

such as ramp up and termination of the source whenever a marine mammal

entered a pre-set ZOI was not required as part of the Letter of

Authorization. Because (1) the SYU 160 dB ZOI can be adequately

monitored visually from the bridge of the survey vessel, (2) aerial

marine mammal surveys may result in additional incidental harassment of

marine mammals, (3) mitigation measures imposed will ensure no

harassment takings of pinnipeds and odontocetes nor any TTS injury to

mysticetes will occur, and (4) the relative low abundance of marine

mammals in the Southern California Bight (SCB) during this time of

year, NMFS does not believe that aerial monitoring of the SYU survey

area is warranted solely for monitoring purposes. However, because

aerial surveys can provide valuable information on whale behavior and

can provide a platform for better statistical analyses of behavioral

modification, NMFS recommends that Exxon incorporate an aerial survey

for marine mammals that provides statistically valid results.

Comment 9. Two commenters recommended that the observers on board

the Exxon vessel either be NMFS employees or be an independent third

party contracted by NMFS.

Response. Although NMFS will require Exxon to have an NMFS employee

on board the vessel after December 15th to observe gray whale behavior,

NMFS has neither the staff nor funding to provide observers under small

take authorizations. For this authorization, Exxon has contracted an

independent firm in southern California to provide NMFS-approved

observers. These observers are trained and instructed to record all

observations made on marine mammals (and other sea life), including

times when marine mammals may enter a designated safety zone. NMFS will

require observers to report daily on harassment takes and logbooks be

submitted as part of the reporting requirement. These logbooks will be

reviewed by NMFS and if violations to either the incidental harassment

authorization or the MMPA are found, appropriate action can be taken

under existing procedures.

Comment 10. Several commenters recommended that (a) because sperm

whales and some other species have long dive periods, monitoring

commence sooner than 30 minutes prior to turning on the array, (b) that

monitoring continue 24 hours daily and (c) NMFS and Exxon supplement

the proposed monitoring program with acoustic monitoring capable of

detecting submerged sperm whales and other cetacean species.

Response. NMFS has modified the monitoring program requirements to

make clear that monitoring will be continuous during daylight hours to

(a) ensure that no marine mammals enter the safety zones while the

array is at or above 160 dB, and (b) commence monitoring 30 minutes

prior to the estimated time that the array will reach the 160 dB SPL.

As the ramp-up period has been increased to approximately 15 minutes,

this will mean a minimum monitoring period of 45 minutes. To ensure

adequate monitoring of the safety zone, Exxon will be required, as part

of the authorization, to provide Big Eye binoculars for use by the

observers.

During nighttime hours, monitoring by the observer needs to be

conducted only whenever the array is being powered up. To facilitate

observations

[[Page 53759]]

within the expanded safety zones, Exxon will provide observers with

night-vision binoculars. The 500-ft (91.5 m) safety zone around the

array will be required to be visually monitored by the biological

observer for a minimum of 30 minutes prior to reaching the 160 dB SPL

during ramp up to ensure that no marine mammals are within the zone.

After careful consideration, additional visual monitoring by the

observer during nighttime is viewed as being neither necessary nor

practical, since, as mentioned previously, it is very unlikely that a

marine mammal will enter the safety zone(s) and ramping up will allow

affected marine mammals adequate time to leave the area. Use of

statistical analyses will allow for an estimate of those mysticetes

that may enter the 160-dB ZOI during nighttime. However, a crew member

will be assigned to monitor the area with instructions to alert the

watch stander to the presence of marine mammals and, if necessary,

power-down the source to below 160 dB. The biological observer on call

for such an event will then be promptly notified.

Because the seismic array is broadband in the same frequencies

utilized by the mysticete cetacean species, it is difficult to make

continuous acoustic recordings of mysticete vocalizations and to

distinguish marine mammal vocalizations from other noises. However,

although recordings can be made independent of the survey vessel's

hydrophone array during periods between transmission cycles or while

turning or maneuvering, because (1) there is an authorization to

incidentally harass mysticete whales; (2) the 160 dB ZOI and the 180

and 190 dB safety zones can be adequately monitored visually from the

bridge of the survey vessel because of the small areas involved; (3)

mitigation measures (including ramp up and termination of the source

whenever marine mammals are sighted within their safety zones) imposed

will virtually eliminate any harassment takings of pinnipeds and

odontocetes and any TTS injury to mysticetes, and (4) the relative low

abundance of marine mammals in the SCB during this time of year

especially deep diving sperm whales, NMFS does not believe that a

sophisticated acoustic monitoring of the SYU survey area is warranted

solely for monitoring purposes. However, because acoustic monitoring

can provide valuable information on whale behavior (at least acoustic)

and an indication of behavioral modification with and without seismic

noise, NMFS recommends that Exxon incorporate an acoustical measurement

program for marine mammals.

National Environmental Policy Act Concerns

Comment 11. Two commenters were concerned that there did not appear

to be a recognition of National Environmental Policy Act (NEPA)

responsibilities since it was not mentioned in the proposed

authorization.

Response. The responsibility for reviewing an activity under NEPA

belongs primarily to the responsible Federal agency, if that activity

is Federal, federally-funded, or federally-permitted. The MMS of the

U.S. Department of the Interior has published several documents under

NEPA regarding offshore oil and gas leasing and development in the SYU.

A list of MMS' NEPA references is available upon request (see

ADDRESSES). In addition, an EA on conducting the 3-D seismic survey in

the SYU has recently been released by, and is available from, MMS (see

ADDRESSES). That document, which has been reviewed and adopted in part

(marine mammals) by NMFS, supports NMFS' conclusion that this activity

will have a negligible impact on marine mammal stocks and their

habitat. An analysis of concerns regarding oil spills and other

environmental issues can be found in those documents.

In addition, it should be noted that while each proposed incidental

harassment authorization is reviewed independently by NMFS to determine

its impact on the human environment, NMFS believes that, because the

finding required for incidental harassment authorizations is that the

taking (limited to harassment) have only a negligible impact on marine

mammals and their habitat, the majority of the authorizations should be

categorically excluded (as defined in 40 CFR 1508.4) from the

preparation of either an environmental impact statement or an EA under

NEPA and section 6.02.c.3(i) of NOAA Administrative Order 216-6 for

Environmental Review Procedures (published August 6, 1991). For Exxon's

application, NMFS conducted a review of the impacts expected from the

issuance of an incidental harassment authorization. NMFS has determined

that there will be no more than a negligible impact on marine mammals

from the issuance of the harassment authorization provided the

mitigation measures required under that authorization are implemented

and, based upon this determination and the portions of the MMS EA

adopted by NMFS, has made a finding of no significant impact.

A programmatic EA on issuing incidental harassment authorizations

under section 101(a)(5)(D) of the MMPA is available for public review

and comment until October 16, 1995 (see ADDRESSES).

Other Concerns

Comment 12. Several commenters recommended NMFS require the

immediate suspension of operations if taking by means other than

harassment occurs as a condition of the authorization.

Response. NMFS concurs with this recommendation and has made the

harassment, injury or death of a marine mammal that is not authorized,

or the serious injury or death of a species for which an authorization

has been issued, to be a violation of the authorization and making the

Incidental Harassment Authorization subject to suspension.

Comment 13. One commenter requested NMFS deny the incidental

harassment authorization because the commenter is opposed to more oil

wells and platforms going into operation, and because the risk of oil

spills is significant.

Response. NMFS would like to clarify that it does not authorize the

activity (i.e., conducting the seismic survey); such authorization is

provided by the MMS and is not within the jurisdiction of the Secretary

of Commerce. Rather, NMFS authorizes the unintentional incidental

harassment of marine mammals in connection with such activities and

prescribes methods of taking and other means of effecting the least

practicable adverse impact on the species and its habitat.

Furthermore, the 3-D seismic survey does not involve any oil

drilling or production activities. The survey merely would provide

additional subsurface data that would enable Exxon to more accurately

assess the oil-bearing strata to more efficiently develop the field

while minimizing the number of wells needed to do so. Geological and

geophysical work to gather seismic data is authorized by Exxon's lease.

The Exxon SYU project underwent considerable environmental analysis

during the implementation of the NEPA process and that analysis

identified mitigation measures that would reduce the risk of oil spills

to the extent feasible. These mitigation measures have been

implemented. Additionally, in complying with recent state and Federal

legislation, Exxon has implemented extensive oil spill contingency

planning requirements that further reduce the risk of oil spills.

[[Page 53760]]

Summary of Mitigation Measures

To minimize potential serious injury to marine mammals and to limit

incidental harassment to the lowest practical level, NMFS will require

Exxon to: (1) Ramp up airguns to operating levels at a rate not to

exceed 6 dB/min. from 160 dB to operating level at the start of

operations or testing, when beginning a new trackline, or any time

after the array is powered down below 160 dB; (2) immediately power

down the array to a level below 160 dB whenever a marine mammal is

observed entering either the 500-ft (152.4 m) safety zone for pinnipeds

and odontocetes or the 1,476 ft (450 m) safety zone for mysticetes; (3)

if marine mammals are observed within these safety zones, powering up

the array above 160 dB must be delayed until all marine mammals are

given the opportunity to leave the safety zone; and (4) ensure that the

seismic survey's acoustical sounds do not impede the southbound

migration of the gray whale. To accomplish this latter mitigation

measure, Exxon will be required to notify NMFS if the survey continues

after December 15, 1995, in order for an NMFS biologist to board an

Exxon vessel to observe gray whale behavior, and to determine if a more

than negligible impact on gray whale migration is occurring. At any

time the NMFS biologist can no longer make a negligible impact

determination for gray whales, Exxon will be required to either

terminate the survey or move to an area of the SYU where a negligible

impact determination can again be made. In addition, no incidental

harassment takings will be authorized after December 31, 1995.

Monitoring

NMFS will require that the holder of the Incidental Harassment

Authorization monitor the impact of seismic activities on the marine

mammal populations within the SYU. Monitoring will be conducted by one

or more NMFS-approved observers during all daylight hours using Big Eye

binoculars and whenever the array is being powered up. At all times,

but specifically during routine nighttime surveys when an observer need

only be on standby, the crew is to be instructed to keep watch for

marine mammals. If any are sighted, the watch-stander is to immediately

notify the NMFS-approved observer. If the marine mammal is within the

safety zone, the acoustic source must be immediately powered down. To

facilitate nighttime sightings within the safety zones, high intensity

lighting will be installed and used to light up these zones.

Visual monitoring will commence a minimum of 30 minutes prior to

the estimated time that the array will reach the 160 dB SPL after being

turned on and/or powered up. Monitoring will consist of noting the

numbers and species of all marine mammals seen within the 2.84 nm (5.2

km) ZOI, their behavior whenever the seismic source is off (speed,

direction, submergence time, respiration etc) and any behavioral

responses or modifications of these indicators due either to the

seismic array or vessel. A report on this monitoring program will be

required to be submitted daily by radio, cellular telephone, or fax to

NMFS and within 90 days of completion of the survey. In addition, NMFS

will require Exxon, as part of the authorization, to undertake

additional observations or measurements, or both, necessary to

determine the acoustic properties of the seismic source and the impacts

of seismic activities on marine mammals. These may include aerial

observations and acoustic recordings of marine mammal vocalizations and

are subject to the approval of NMFS prior to initiating the survey.

Consultation

Under section 7 of the Endangered Species Act (16 U.S.C. 1531 et

seq.), NMFS has completed consultation on the issuance of this

authorization. Based on the best available information, NMFS concludes

that the authorization to harass small numbers of cetaceans from

conducting a 3-D seismic survey in the SYU under section 101(a)(5)(D)

of the MMPA is not likely to jeopardize the continued existence of any

listed species. The short-term impact from conducting these surveys may

result in a temporary modification in behavior of certain listed and

non-listed whale species. While temporary behavioral modifications may

be made by these species of cetaceans to avoid seismic noise, this

behavioral change is expected to have only a negligible impact on the

animals.

Conclusions

Since NMFS is assured that the taking will not result in more than

the incidental harassment (as defined by the MMPA Amendments of 1994)

of small numbers of mysticete cetaceans, sperm whales, and possibly

pygmy sperm whales; would have only a negligible impact on these

cetacean stocks; will not have an unmitigable adverse impact on the

availability of these stocks for subsistence uses; and would result in

the least practicable impact on the stocks, NMFS has determined that

the requirements of section 101(a)(5)(D) have been met and the

authorization can be issued.

For the above reasons, NMFS has issued an incidental harassment

authorization for the period ending December 31, 1995, for a 3-D

seismic survey within the SYU provided the above mentioned monitoring

and reporting requirements are incorporated.

Dated: October 11, 1995.

Patricia A. Montanio,

Acting Director, Office of Protected Resources, National Marine

Fisheries Service.

[FR Doc. 95-25722 Filed 10-16-95; 8:45 am]

BILLING CODE 3510-22-P