Takes of Marine Mammals Incidental to Specified Activities; Navy Training Conducted at the Silver Strand Training Complex, San Diego Bay, 64276-64295 [2010-26286]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 75, Number 201 (Tuesday, October 19, 2010)]
[Notices]
[Pages 64276-64295]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-26286]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XZ14


Takes of Marine Mammals Incidental to Specified Activities; Navy 
Training Conducted at the Silver Strand Training Complex, San Diego Bay

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

ACTION: Notice; proposed incidental harassment authorization; request 
for comments.

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SUMMARY: NMFS has received an application from the U.S. Navy (Navy) for 
an Incidental Harassment Authorization (IHA) to take marine mammals, by 
harassment, incidental to conducting training exercises at the Silver 
Strand Training Complex (SSTC)

[[Page 64277]]

in the vicinity of San Diego Bay, California. Pursuant to the Marine 
Mammal Protection Act (MMPA), NMFS is requesting comments on its 
proposal to issue an IHA to the Navy to incidentally harass, by Level B 
Harassment only, four species of marine mammals during the specified 
activity.

DATES: Comments and information must be received no later than November 
18, 2010.

ADDRESSES: Comments on the application should be addressed to Michael 
Payne, Chief, Permits, Conservation and Education Division, Office of 
Protected Resources, National Marine Fisheries Service, 1315 East-West 
Highway, Silver Spring, MD 20910-3225. The mailbox address for 
providing e-mail comments is 0648-XZ14@noaa.gov. NMFS is not 
responsible for e-mail comments sent to addresses other than the one 
provided here. Comments sent via e-mail, including all attachments, 
must not exceed a 10-megabyte file size.
    Instructions: All comments received are a part of the public record 
and will generally be posted to https://www.nmfs.noaa.gov/pr/permits/incidental.htm without change. All Personal Identifying Information 
(for example, name, address, etc.) voluntarily submitted by the 
commenter may be publicly accessible. Do not submit Confidential 
Business Information or otherwise sensitive or protected information.
    A copy of the application containing a list of the references used 
in this document may be obtained by writing to the address specified 
above, telephoning the contact listed below (see FOR FURTHER 
INFORMATION CONTACT), or visiting the Internet at: https://www.nmfs.noaa.gov/pr/permits/incidental.htm. Documents cited in this 
notice may also be viewed, by appointment, during regular business 
hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT: Shane Guan, Office of Protected 
Resources, NMFS, (301) 713-2289, ext 137.

SUPPLEMENTARY INFORMATION:

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce (Secretary) to allow, upon request, 
the incidental, but not intentional taking of small numbers of marine 
mammals by U.S. citizens who engage in a specified activity (other than 
commercial fishing) if certain findings are made and regulations are 
issued or, if the taking is limited to harassment, notice of a proposed 
authorization is provided to the public for review.
    Authorization for incidental takings shall be granted if NMFS finds 
that the taking will have a negligible impact on the species or 
stock(s), will not have an unmitigable adverse impact on the 
availability of the species or stock(s) for subsistence uses (where 
relevant), and if the permissible methods of taking and requirements 
pertaining to the mitigation, monitoring and reporting of such taking 
are set forth. NMFS has defined ``negligible impact'' in 50 CFR 216.103 
as: `` * * * an impact resulting from the specified activity that 
cannot be reasonably expected to, and is not reasonably likely to, 
adversely affect the species or stock through effects on annual rates 
of recruitment or survival.''
    The National Defense Authorization Act of 2004 (NDAA) (Pub. L. 108-
136) removed the ``small numbers'' and ``specified geographical 
region'' limitations and amended the definition of ``harassment'' as it 
applies to a ``military readiness activity'' to read as follows 
(Section 3(18)(B) of the MMPA):
    (i) Any act that injures or has the significant potential to injure 
a marine mammal or marine mammal stock in the wild [Level A 
Harassment]; or
    (ii) Any act that disturbs or is likely to disturb a marine mammal 
or marine mammal stock in the wild by causing disruption of natural 
behavioral patterns, including, but not limited to, migration, 
surfacing, nursing, breeding, feeding, or sheltering, to a point where 
such behavioral patterns are abandoned or significantly altered [Level 
B Harassment].
    Section 101(a)(5)(D) of the MMPA established an expedited process 
by which citizens of the United States can apply for an authorization 
to incidentally take small numbers of marine mammals by harassment. 
Section 101(a)(5)(D) establishes a 45-day time limit for NMFS review of 
an application followed by a 30-day public notice and comment period on 
any proposed authorizations for the incidental harassment of marine 
mammals. Within 45 days of the close of the comment period, NMFS must 
either issue or deny the authorization.

Summary of Request

    NMFS received an application on March 3, 2010, from the Navy for 
the taking, by harassment, of marine mammals incidental to conducting 
training exercises at the Navy's Silver Strand Training Complex (SSTC) 
in the vicinity of San Diego Bay, California, starting late November 
2010. After addressing comments from NMFS, the Navy modified its 
application and submitted a revised application on September 13, 2010. 
The September 13, 2010, application is the one available for public 
comment (see ADDRESSES) and considered by NMFS for this proposed IHA.

Description of the Specific Activity

    The Navy has been training and operating in the SSTC for over 60 
years. The land, air, and sea spaces of the SSTC have provided, and 
continue to provide, a safe and realistic training environment for 
naval forces charged with defense of the Nation. The SSTC, Figure 1-1 
of the Navy's IHA application, is located south of the City of 
Coronado, California and north of the City of Imperial Beach, 
California. It is composed of ocean and bay training lanes, adjacent 
beach training areas, ocean anchorages, and inland training areas. To 
facilitate range management and scheduling, SSTC is divided into 
numerous training sub-areas (Figure 1-1 of the Navy's IHA application). 
In-water training sub-areas include: The ocean side of the SSTC divided 
into two non-contiguous areas, SSTC-NORTH (Boat Lanes 1-10) and SSTC-
SOUTH (Boat Lanes 11-14); SSTC-NORTH also includes south San Diego Bay 
in-water training areas, designated Alpha through Hotel and the Lilly 
Ann Drop Zone.
    The Navy's mission is to maintain, train, and equip combat-ready 
naval forces capable of winning wars, deterring aggression, and 
maintaining freedom of the seas. Title 10, U.S. Code Section 5062 
directs the Chief of Naval Operations to train all naval forces for 
combat. The Chief of Naval Operations meets that direction, in part, by 
conducting littoral training exercises and ensuring naval forces have 
access to ranges where they can develop and maintain skills for wartime 
missions. The Navy is proposing the following at SSTC: Continue current 
training, increase training tempo and types of training, conduct 
existing routine training at additional locations within SSTC 
established training areas, construct a demolition pit on inland 
training areas, and increase access availability of existing beach and 
inland training areas.
    The Navy has conducted a review of its continuing and proposed 
training conducted at SSTC to determine whether there is a potential 
for harassment of marine mammals. The following discussion describes 
the underwater detonation training and pile driving conducted at SSTC. 
Other training events conducted at SSTC, which are not anticipated to 
rise to the level of harassment to marine mammals

[[Page 64278]]

as defined under the MMPA, are more completely described in the SSTC 
Draft Environmental Impact Statement.

Underwater Detonations

    Underwater detonations are conducted by Explosive Ordnance Disposal 
(EOD) units, Naval Special Warfare (NSW) units, MH-60S Mine 
Countermeasure helicopter squadrons, and Mobile Diving and Salvage 
units at the SSTC. The training provides Navy personnel with hands-on 
experience with the design, deployment, and detonation of underwater 
clearance devices of the general type and size that they are required 
to understand and utilize in combat. EOD groups conduct most of the 
underwater detonation training at SSTC as part of their training in the 
detection, avoidance, and neutralization of mines to protect Navy ships 
and submarines, and offensive mine laying in naval operations.
    For safety reasons, underwater detonation training only occurs 
during daylight and can only be conducted in sea-states of up to 
Beaufort 3 (presence of large wavelets, crests beginning to break, 
presence of glassy foam, and/or perhaps scattered whitecaps). Table 1 
describes the types of underwater detonation training events conducted 
within the SSTC.

  Table 1--Detailed Descriptions of SSTC Underwater Detonation Training
                                 Events
------------------------------------------------------------------------
   Training duration/event                    Description
------------------------------------------------------------------------
Shock Wave Action Generator    SWAG is a tool used by Explosive Ordnance
 (SWAG).                        Disposal (EOD) to disarm enemy limpet
1 day........................   mines which have been attached to the
                                hull of a ship. The SWAG is composed of
                                a cylindrical steel tube, 3 inches long
                                and 1 inch wide, containing
                                approximately 0.033 lbs of explosives.
                                The single explosive charge is highly
                                focused. For SWAG training, a metal
                                sheet containing an inert mine is
                                lowered from the side of a small vessel,
                                or small boat. Divers place a single
                                SWAG on the mine that is located mid-
                                water column, within water depths of 10-
                                20 feet. A bag is placed over the mine
                                to catch falling debris.
Mine Counter Measure.........  Events are performed from a small craft
1 day........................   to locate and identify suspected
                                ordnance either at mid-column or on the
                                sea floor at a water depth of <= 72
                                feet. A detachment dives to locate the
                                suspected ordnance. Once located, a
                                single explosive charge (10-20 lbs NEW)
                                is placed next to the ordnance to
                                neutralize it. The neutralized mine is
                                then raised, towed to shore, and
                                beached.
Floating Mine................  Personnel are inserted into the ocean via
1 day........................   helicopter or 24-foot vessel, swim to
                                the floating mine in water depths of
                                less than 72 feet, and place a single
                                explosive countercharge (less than 5 lbs
                                NEW) on the mine. The team retreats a
                                safe distance prior to command
                                detonation of a single countercharge.
Dive Platoon.................  Divers are inserted into the ocean via
1 day........................   helicopter or 24-foot vessel, dive to
                                depths of 30-72 feet and detonate
                                sequential charges on an inert mine
                                shape placed on the bottom with 3.5 lbs
                                NEW.
Very Shallow Water Mine        Locating, identifying, and neutralizing
 Counter Measure.               mines (placing explosives on mines for
1 day........................   the purposes of destroying them) placed
                                either mid-column or on the sea floor at
                                a water depth of <= 24 feet (10-20 lbs
                                NEW). Use of explosives will occur
                                during approximately 60% of training
                                events and will ONLY occur in the SSTC
                                oceanside Boat Lanes. All in-Bay
                                training (40%) will not use any
                                explosives. Personnel are transported to
                                a location in one to two RHIBs and place
                                transponders into the water. The
                                transponders hover over the bottom to
                                provide divers with shallow-water
                                navigation instruction.
Unmanned Underwater Vehicle    Training on use of UUVs. One to two RHIBs
 (UUV).                         are used to transport personnel to a
1 day........................   site. Two transponders are placed in the
                                water, with an UUV between them. UUVs
                                explore the area, photograph, and
                                collect hydrographic information. After
                                analysis is complete, appropriate Navy
                                marine mammals are dispatched to
                                localize and mark potential objects,
                                followed by divers who clear the area of
                                identified hazards. Approximately 3% of
                                events involve placing a single 10-15
                                lbs NEW charge in water depths from 10
                                to 72 feet on the oceanside of SSTC-
                                NORTH (on the bottom or up to 20 feet
                                from the surface) to neutralize a
                                simulated mine. Use and detonation of
                                explosives will only occur in the SSTC
                                oceanside Boat Lanes 1-14. Bayside UUV
                                use in the Bay will be for operator
                                training and not contain explosives.
MK8 Marine Mammal/Marine       Navy divers work with the help of the
 Mammal Systems (MMS).          Navy's trained marine mammals to detect
1 day........................   underwater objects. Approximately 10% of
                                training involves the setting of a 13-
                                or 29 lbs NEW charge to detonate the
                                objects. Sequential detonations operate
                                at water depths of 10 to 72 feet and are
                                bottom laid. Single charges are laid
                                within water depths of 24 to 72 feet, 20
                                feet from the surface or below. Use of
                                explosives will only occur in the SSTC
                                oceanside Boat Lanes 1-14.
Mine Neutralization..........  Personnel are inserted via helicopter or
                                vessel for underwater demolition
                                training consisting of eight sequential
                                charges placed on the sea floor using
                                3.5 lbs NEW explosive charges on various
                                inert mine shapes in water depths of 30
                                to 72 feet to maintain qualifications.
Surf Zone Test Detachment      To support clearance capability in the
 Equipment T&E.                 surf zone (out to 10 feet of water), EOD
1 day........................   would test and evaluate the
                                effectiveness of new detection and
                                neutralization equipment (i.e.,
                                generally explosive counter-techniques
                                to safely disarm/render safe mines) in
                                surf conditions. Use of explosives will
                                occur during 1% of training events (0.1
                                to 20 lbs NEW) and will only occur in
                                the SSTC oceanside Boat Lanes 1-14.
Unmanned Underwater Vehicle    Training consists of placing 2 sequential
 Neutralization.                charges consisting of a Seafox (3.3 lbs)
1 day........................   or Archerfish (3.57 lbs) charge placed
                                from depths of 10 feet to the bottom in
                                water depth less than 72 feet.
Airborne Mine Neutralization   The training would involve an MH-60S
 System (AMNS).                 helicopter deploying an AMNS underwater
1 day........................   vehicle into the water that searches
                                for, locates, and destroys mines. The
                                vehicle is self-propelled and unmanned.
                                Approximately 20% of the training would
                                involve the AMNS being remotely
                                detonated (3.5 lbs NEW) when it
                                encounters a simulated (inert) mine
                                shape.
Naval Special Warfare          Demolition Requalifications and Training
 Underwater Demolition          provides teams with experience in
 Qualification/Certification.   underwater detonations by conducting
1 day........................   detonations on metal plates near the
                                shoreline. At water depths of 10 to 72
                                feet two sequential 12.5-13.75 lbs NEW
                                charges are placed on the bottom or a
                                single 25.5 lbs charge is placed from a
                                depth of 20 feet to the bottom.
Naval Special Warfare          Up to 40 persons participate in the
 Underwater Demolition          activity, which involves small groups
 Training.                      swimming to shore from four inflatable
1 day........................   boats located approximately 1,000 yards
                                offshore; boats may be beached on shore.
                                A single charge of less than 10 lbs NEW
                                (if detonated on the bottom) or less
                                than 3.6 lbs NEW (if within five feet of
                                the surface) is manually detonated near
                                the shoreline in water less than 24 feet
                                deep.

[[Page 64279]]

 
SEAL Delivery Vehicle/         Designed to certify SDV Team operators
 Advanced SEAL Delivery         for deployment, events include direct
 System Certification to        action, reconnaissance, and/or counter-
 Deploy.                        terrorism events. Training may include
14 days......................   navigation runs into and out of the San
                                Diego Bay, hydrographic reconnaissance,
                                over the beach (OBT) training, combat
                                swimmer, and underwater detonation
                                training. Based on training tempo,
                                multiple events could occur. Underwater
                                detonation events involve a single timed
                                charge of 10 lbs or less NEW in water
                                depths of 24 feet or less placed from
                                mid-water column to the seafloor that
                                may be conducted in coordination with
                                other training events. Use of explosives
                                will only occur in the SSTC oceanside
                                Boat Lanes 1-10. The whole Certification
                                process is a 14 day evolution, although
                                explosives would not be used every day.
------------------------------------------------------------------------

    Table 2 shows the underwater detonation training event types 
described above along with the net equivalent weight (NEW) for the 
charges involved, water depth, and number of events per year. NEW is a 
conversion that allows the comparison of different mixes of explosive 
formulas. Since different explosive formulas may have different 
explosive potentials, explosive potentials are often normalized and 
expressed as compared to the equivalent explosive potential of TNT 
(trinitrotoluene). While explosive NEW shown in Table 2 range from 0.03 
lbs to 29 lbs, it should be noted that approximately 78% of the annual 
underwater detonation training events at the SSTC would use explosive 
weights less than 10 lbs (see Figure 2-2 of the Navy's IHA 
application).

                                                    Table 2--SSTC Annual Underwater Explosive Events
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                         No. of
 Underwater detonation training        NEW  (lbs)       No. of  sequential   Water depth (feet)     Charge depth        training        SSTC  location
              event                                        detonations                                                 events/yr*
--------------------------------------------------------------------------------------------------------------------------------------------------------
Shock wave action generator       0.033..............  1/det..............  10-20..............  Mid-water.........              74  SDB.**
 (SWAG).
Shock wave action generator       0.033..............  1/det..............  10-20..............  Mid-water.........              16  Oceanside.
 (SWAG).
Mine Counter Measure............  10-20..............  1/det..............  <= 72..............  Mid-water.........              29  Oceanside.
Mine Counter Measure............  10-20..............  1/det..............  <= 72..............  Bottom............              29  Oceanside.
Floating Mine...................  <= 5...............  1/det..............  <= 72..............  Surface (< 5 ft)..              53  Oecanside.
Dive Platoon....................  3.5................  1/det..............  39-72..............  Bottom............               8  Oceanside.
Very Shallow Water Mine Counter   0.1-20.............  1/det..............  <= 24..............  Bottom............              60  Oceanside.
 Measure.
Unmanned underwater vehicle.....  10-15..............  1/det..............  10-72..............  Bottom to 10 ft                  4  Oceanside.
                                                                                                  from surface.
Marine Mammal System............  13 & 29............  2/det..............  10-72..............  Bottom............               8  Oceanside.
Marine Mammal System Operator     13 & 29............  1/det..............  24-72..............  Bottom to 20 ft                  8  Oceanside.
 Course.                                                                                          from surface.
Mine Neutralization.............  3.5................  8/det..............  30-72..............  Bottom............               4  Oceanside.
Surf Zone Testing and Evaluation  to 20..............  1/det..............  <= 24..............  Bottom............               2  Oceanside.
Unmanned Underwater Vehicle       3.3 & 3.57.........  2/det..............  10-72..............  Bottom to 10 ft                  4  Oceanside.
 Neutralization.                                                                                  from surface.
Airborne Mine Neutralization      3.53...............  1/det..............  40-72..............  Mid-water to                    10  Oceanside.
 System.                                                                                          bottom.
Qualification/Certification.....  12.5-13.75.........  2/det..............  10-72..............  Bottom............               8  Oceanside.
Qualification/Certification.....  25.5...............  1/det..............  40-72..............  Bottom to 20 ft                  4  Oceanside.
                                                                                                  from surface.
Naval Special Warfare Demolition  <= 10..............  1/det..............  <= 24..............  Bottom............               4  Oceanside.
 Training.
Naval Special Warfare Demolition  <= 3.6.............  1/det..............  <= 24..............  Surface...........               8  Oceanside.
 Training.
SEAL Delivery Vehicle/Advance     <= 10..............  1/det..............  <= 24..............  Bottom to mid-                  40  Oceanside.
 SEAL Delivery Vehicle.                                                                           water.
--------------------------------------------------------------------------------------------------------------------------------------------------------
* No. of training events is the total amount of underwater detonation training involving each particular Training Event Type. Most Training events are a
  single detonation (i.e., 1/detonation) per event. However, four of these Training Event Types involve sequential charges during the same training
  event. Sequential charges are either conducted with a 10-second delay between detonations or 30-minute delay between detonations.
** San Diego Bay.

Elevated Causeway System (ELCAS) Training

    Elevated Causeway System (ELCAS) is a modular pre-fabricated 
causeway pier. ELCAS provides a link between offshore amphibious supply 
ships with associated lighterage (i.e., small cargo boats and barges) 
and the shore by bridging the surf zone. Offloaded vehicles and 
supplies can be driven on the causeway to and from shore.
    ELCAS events would occur up to four times a year at either the 
dedicated training lane within bayside Bravo Beach, or in the oceanside 
training lanes at SSTC-North. During ELCAS training events, 24-inch 
wide hollow steel piles are driven into the sand in the surf zone with 
an impact hammer. Pile installation occurs over a period of 
approximately 10 days and pile removal over approximately three days. 
Approximately 101 piles are driven into the beach and surf zone with a 
diesel impact hammer over the course of approximately 10 days, 24 hours 
a day (i.e., during the day and night). Each pile takes an average of 
10 minutes to install, with around 250 to 300 impacts per pile. Pile 
driving includes a semi-soft start as part of the normal operating 
procedure based on the design of the drive equipment. The pile driver 
increases impact strength as resistance goes up. At first, the pile 
driver piston

[[Page 64280]]

drops a few inches. As resistance goes up, the pile driver piston will 
drop from a higher distance thus providing more impact due to gravity. 
The pile driver can take 5 to 7 minutes to reach full impact strength. 
As sections of piles are installed, causeway platforms are then hoisted 
and secured onto the piles with hydraulic jacks and cranes. The ELCAS 
is then used for a period of time, usually less than two weeks to 
transfer cargo back and forth from sea to shore.
    At the end of all the ELCAS training, a vibratory hammer attached 
to the pile head will be used to remove piles by applying a rapidly 
alternating force to the pile by rotating eccentric weights about 
shafts, resulting in an upward vibratory force on the pile. The 
vertical vibration in the pile disturbs or ``liquefies'' the sediment 
next to the pile causing the sediment particles to lose their 
frictional grip on the pile. This also allows sediment to fill back 
into the hole that is left after the pile is removed. Removal takes 
approximately 15 minutes per pile over a period of around 3 days.
    In relation to this IHA application, installation and removal of 
ELCAS support piles were deemed by the Navy to most likely have the 
potential to harass marine mammals.

Other Training

    In addition to underwater detonations and ELCAS, the Navy performs 
a variety of other shallow water and amphibious training at SSTC. This 
training includes amphibious vessel and vehicle maneuvering, beach 
landings, causeway (floating pier) insertions onto the beach, swimming, 
land demolitions, transfer of fluids from vessel to the shore through a 
flexible conduit (seawater is used as the fluid during training), and 
helicopter overflight events.
    Potential impacts from other training applicable to marine mammals 
included helicopter overflights, and marine boat and vessel movement 
within the SSTC. However, as discussed in detail in the Navy's IHA 
application, the Navy determined that only underwater detonations and 
ELCAS pile driving and pile removal training events at SSTC have the 
potential to rise to the level of harassment as defined under the MMPA, 
as amended in 1994. NMFS agrees with the Navy's determination.

Description of Marine Mammals in the Area of the Specified Activity

    There are four marine mammal species within SSTC marine waters with 
confirmed or historic occurrence in the study area. These include the 
California sea lion (Zalophus californianus), Pacific harbor seal 
(Phoca vitulina richardsii), California coastal stock of bottlenose 
dolphin (Tursiops truncatus), and more infrequently gray whale 
(Eschrichtius robustus). None are listed as threatened or endangered 
under the Endangered Species Act (ESA).
    The Navy's IHA application contains information on the status, 
distribution, seasonal distribution, and abundance of each of the 
species under NMFS jurisdiction mentioned in this document. Please 
refer to the application for that information (see ADDRESSES). 
Additional information can also be found in the NMFS Stock Assessment 
Reports (SAR). The Pacific 2009 SAR is available at: https://www.nmfs.noaa.gov/pr/pdfs/sars/po2009.pdf.

California Sea Lions

    The California sea lion is by far the most commonly-sighted 
pinniped species at sea or on land in the vicinity of the SSTC. Nearly 
all of the U.S. Stock (more than 95%) of California sea lion breeds and 
gives birth to pups on San Miguel, San Nicolas, and Santa Barbara 
islands off California. Smaller numbers of pups are born on the 
Farallon Islands, and A[ntilde]o Nuevo Island (Lowry et al. 1992). In 
California waters, sea lions represented 97% (381 of 393) of identified 
pinniped sightings at sea during the 1998-1999 NMFS surveys (Carretta 
et al. 2000). They were sighted during all seasons and in all areas 
with survey coverage from nearshore to offshore areas (Carretta et al. 
2000).
    Survey data from 1975 to 1978 were analyzed to describe the 
seasonal shifts in the offshore distribution of California sea lions 
(Bonnell and Ford 1987). During summer, the highest densities were 
found immediately west of San Miguel Island. During autumn, peak 
densities of sea lions were centered on Santa Cruz Island. During 
winter and spring, peak densities occurred just north of San Clemente 
Island. The seasonal changes in the center of distribution were 
attributed to changes in the distribution of the prey species. If 
California sea lion distribution is determined primarily by prey 
abundance as influenced by variations in local, seasonal, and inter-
annual oceanographic variation, these same areas might not be the 
center of sea lion distribution every year. Costa et al. (2007) was 
able to indentify kernel home range contours for foraging female sea 
lions during non-El Nino conditions, although there was some variation 
over the three years of this tagging study. Melin et al. (2008) showed 
that foraging female sea lions showed significant variability in 
individual foraging behavior, and foraged farther offshore and at 
deeper depths during El Nino years as compared to non-El Nino years. 
The distribution and habitat use of California sea lions vary with the 
sex of the animals and their reproductive phase. Adult males haul out 
on land to defend territories and breed from mid-to-late May until late 
July. The pupping and mating season for sea lions begins in late May 
and continues through July (Heath 2002). Individual males remain on 
territories for 27-45 days without going to sea to feed. During August 
and September, after the mating season, the adult males migrate 
northward to feeding areas as far away as Washington (Puget Sound) and 
British Columbia (Lowry et al. 1992). They remain there until spring 
(March-May), when they migrate back to the breeding colonies. Thus, 
adult males are present in offshore areas of the SSTC only briefly as 
they move to and from rookeries. Distribution of immature California 
sea lions is less well known, but some make northward migrations that 
are shorter in length than the migrations of adult males (Huber 1991). 
However, most immature sea lions are presumed to remain near the 
rookeries, and thus remain near SSTC for most of the year (Lowry et al. 
1992). Adult females remain near the rookeries throughout the year. 
Most births occur from mid-June to mid-July (peak in late June).
    California sea lions feed on a wide variety of prey, including 
Pacific whiting, northern anchovy, mackerel, squid, sardines, and 
rockfish (Antonelis et al. 1990; Lowry et al. 1991; Lowry and Carretta 
1999; Lowry and Forney 2005; Bearzi 2006). In Santa Monica Bay, 
California sea lions are known to follow and feed near bottlenose 
dolphins (Bearzi 2006), and if in the near shore waters of SSTC, may 
forage on common coastal beach fish species (corbina and barred 
surfperch) as dolphins (Allen 2006).
    There are limited published at-sea density estimates for pinnipeds 
within Southern California. Higher densities of California sea lions 
are observed during cold-water months. At-sea densities likely decrease 
during warm-water months because females spend more time ashore to give 
birth and attend to their pups. Radio-tagged female California sea 
lions at San Miguel Island spent approximately 70% of their time at sea 
during the non-breeding season (cold-water months) and pups spent an 
average of 67% of their time ashore during their mother's absence 
(Melin and DeLong 2000). Different age classes of California sea lions 
are found in the offshore areas of SSTC throughout the year (Lowry et 
al. 1992). Although adult male California sea lions feed in areas

[[Page 64281]]

north of SSTC, animals of all other ages and sexes spend most, but not 
all, of their time feeding at sea during winter, thus, the winter 
estimates likely are somewhat low. During warm-water months, a high 
proportion of the adult males and females are hauled out at terrestrial 
sites during much of the period, so the summer estimates are low to a 
greater degree.
    The NMFS population estimate of the U.S. Stock of California sea 
lions is 238,000 (Carretta et al. 2010), with a minimum estimate based 
on a 2005 shore-based survey of all age and sex classes of 141,842 
(NMFS, unpublished data, Carretta et al. 2010). The California sea lion 
is not listed under the ESA, and the U.S. Stock, some of which occurs 
in the SSTC, is not considered a strategic stock under the MMPA.

Pacific Harbor Seal

    Harbor seals are considered abundant throughout most of their range 
from Baja California to the eastern Aleutian Islands. An unknown number 
of harbor seals also occur along the west coast of Baja California, at 
least as far south as Isla Asuncion, which is about 100 miles south of 
Punta Eugenia. Animals along Baja California are not considered to be a 
part of the California stock because it is not known if there is any 
demographically significant movement of harbor seals between California 
and Mexico (Carretta et al. 2010). Peak numbers of harbor seals haul 
out on land during late May to early June, which coincides with the 
peak of their molt. They generally favor sandy, cobble, and gravel 
beaches (Stewart and Yochem 1994; 2000), and most haul out on the 
central California mainland and Santa Cruz Island (Lowry and Carretta 
2003; Carretta et al. 2010).
    There are limited at-sea density estimates for pinnipeds within 
Southern California. Harbor seals do not make extensive pelagic 
migrations, but do travel 300-500 km on occasion to find food or 
suitable breeding areas (Herder 1986; Carretta et al. 2007). Nursing of 
pups begins in late February, and pups start to become weaned in May. 
Breeding occurs between late March and early May on the southern and 
northern Channel Islands. When at sea during May and June (and March to 
May for breeding females), they generally remain in the vicinity of 
haul-out sites and forage close to shore in relatively shallow waters. 
Based on likely foraging strategies, Grigg et al. (2009) reported 
seasonal shifts in harbor seal movements based on prey availability.
    Harbor seals are opportunistic feeders that adjust their feeding to 
take advantage of locally and seasonally abundant prey which can 
include small crustaceans, rock fish, cusk-eel, octopus, market squid, 
and surfperch (Bigg 1981; Payne and Selzer 1989; Stewart and Yochem 
1994; Stewart and Yochem 2000; Baird 2001; Oates 2005). If in the near 
shore waters of SSTC, harbor seals may forage on common coastal beach 
fish species, such as corbina and barred surfperch (Allen 2006).
    Harbor seals are found in the SSTC throughout the year (Carretta et 
al. 2000) with local densities estimated at 0.010 animals/km\2\ during 
the warm season and 0.020 animals/km\2\ during the cold season.
    Based on the most recent harbor seal counts (26,333 in May-July 
2004, Lowry et al. 2005) and Hanan's revised correction factor, the 
harbor seal population in California is estimated by NMFS to number 
34,233 (Carretta et al. 2010). The minimum size of the California 
harbor seal population is 31,600 (Carretta et al. 2010). Of the 
estimated California population (34,233), less than 30% are thought to 
reside within Southern California due to lack of suitable haul-out 
sites because of significant beach urbanization (Lowry et al. 2008).
    The harbor seal is not listed under the ESA, and the California 
Stock, some of which occurs in the SSTC, is not considered a strategic 
stock under the MMPA. The California population has increased from the 
mid-1960s to the mid-1990s, although the rate of increase may have 
slowed during the 1990s as the population has reached and may be 
stabilizing at carrying capacity (Hanan 1996, Carretta et al. 2010).

Bottlenose Dolphin

    There are two distinct populations of bottlenose dolphins within 
southern California, a coastal population found within 0.5 nm (0.9 km) 
of shore and a larger offshore population (Hansen 1990; Bearzi et al. 
2009). The California Coastal Stock is the only one of these two stocks 
likely to occur within the SSTC. The bottlenose dolphin California 
Coastal Stock occurs at least from Point Conception south into Mexican 
waters, at least as far south as San Quintin, Mexico. In southern 
California, animals are found within 1,600 ft (500 m) of the shoreline 
99% of the time and within 820 ft (250 m) 90% of the time (Hanson and 
Defran 1993). Occasionally, during warm-water incursions such as during 
the 1982-1983 el Ni[ntilde]o event, their range extends as far north as 
Monterey Bay (Wells et al. 1990). Bottlenose dolphins in the Southern 
California Bight (SCB) appear to be highly mobile within a relatively 
narrow coastal zone (Defran et al. 1999), and exhibit no seasonal site 
fidelity to the region (Defran and Weller 1999). There is little site 
fidelity of coastal bottlenose dolphins along the California coast; 
over 80% of the dolphins identified in Santa Barbara, Monterey, and 
Ensenada have also been identified off San Diego (Defran et al. 1999; 
Maldini-Feinholz 1996; Carretta et al. 2008; Bearzi et al. 2009). 
Bottlenose dolphins could occur in the SSTC at variable frequencies and 
periods throughout the year based on localized prey availability 
(Defran et al. 1999).
    The Pacific coast bottlenose dolphins feed primarily on surfperches 
(Family Embiotocidae) and croakers (Family Sciaendae) (Norris and 
Prescott 1961; Walker 1981; Schwartz et al. 1992; Hanson and Defran 
1993), and also consume squid (Loligo opalescens) (Schwartz et al. 
1992). The coastal stock of bottlenose dolphin utilizes a limited 
number of fish prey species with up to 74% being various species of 
surfperch or croakers, a group on non-migratory year-round coastal 
inhabitant (Defran et al. 1999; Allen et al. 2006). For Southern 
California, common croaker prey species include spotfin croaker, 
yellowfin croaker, and California corbina, while common surfperch 
species include barred surfperch and walleye surfperch (Allen et al. 
2006). The corbina and barred surfperch are the most common surf zone 
fish where bottlenose dolphins have been observed foraging (Allen et 
al. 2006). Defran et al. (1999) postulated that the coastal stock of 
bottlenose dolphins showed significant movement within their home range 
(Central California to Mexico) in search of preferred but patchy 
concentrations of near shore prey (i.e., croakers and surfperch). After 
finding concentrations of prey, animals may then forage within a more 
limited spatial extent to take advantage of this local accumulation 
until such time that prey abundance is reduced after which the dolphins 
once again shift location over larger distances (Defran et al. 1999). 
Bearzi (2005) and Bearzi et al. (2009) also noted little site fidelity 
from coastal bottlenose dolphins in Santa Monica Bay, California, and 
that these animals were highly mobile with up to 69% of their time 
spent in travel and dive-travel mode and only 5% of the time in feeding 
behaviors.
    Group size of the California coastal stock of bottlenose dolphins 
has been reported to range from 1 to 57 dolphins (Bearzi 2005), 
although mean pod sizes were around 19.8 (Defran and Weller 1999) and 
10.1 (Bearzi 2005). An at-sea density estimate of 0.202 animals/km\2\ 
was used for acoustic impact modeling for both the warm and cold 
seasons as

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derived in National Center for Coastal Ocean Science (2005).
    Based on photographic mark-recapture surveys conducted along the 
San Diego coast in 2004 and 2005, population size for the California 
Coastal Stock of the bottlenose dolphin is estimated to be 323 
individuals (CV = 0.13, 95% CI 259-430; Dudzik et al. 2005; Carretta et 
al. 2010). This estimate does not reflect that approximately 35% of 
dolphins encountered lack identifiable dorsal fin marks (Defran and 
Weller 1999). If 35% of all animals lack distinguishing marks, then the 
true population size would be closer to 450-500 animals (Carretta et 
al. 2010). The California Coastal Stock of bottlenose dolphins is not 
listed under the ESA, and is not considered a strategic stock under the 
MMPA.

Gray Whale

    The Eastern North Pacific population is found from the upper Gulf 
of California (Tershy and Breese 1991), south to the tip of Baja 
California, and up the Pacific coast of North America to the Chukchi 
and Beaufort seas. There is a pronounced seasonal north-south 
migration. The eastern North Pacific population summers in the shallow 
waters of the northern Bering Sea, the Chukchi Sea, and the western 
Beaufort Sea (Rice and Wolman 1971). The northern Gulf of Alaska (near 
Kodiak Island) is also considered a feeding area; some gray whales 
occur there year-round (Moore et al. 2007). Some individuals spend the 
summer feeding along the Pacific coast from southeastern Alaska to 
central California (Sumich 1984; Calambokidis et al. 1987; 2002). 
Photo-identification studies indicate that gray whales move widely 
along the Pacific coast and are often not sighted in the same area each 
year (Calambokidis et al. 2002). In October and November, the whales 
begin to migrate southeast through Unimak Pass and follow the shoreline 
south to breeding grounds on the west coast of Baja California and the 
southeastern Gulf of California (Braham 1984; Rugh 1984). The average 
gray whale migrates 4,050 to 5,000 nm (7,500 to 10,000 km) at a rate of 
80 nm (147 km) per day (Rugh et al. 2001; Jones and Swartz 2002). 
Although some calves are born along the coast of California (Shelden et 
al. 2004), most are born in the shallow, protected waters on the 
Pacific coast of Baja California from Morro de Santo Domingo (28 
[deg]N) south to Isla Creciente (24 [deg]N) (Urb[aacute]n et al. 2003). 
Main calving sites are Laguna Guerrero Negro, Laguna Ojo de Liebre, 
Laguna San Ignacio, and Estero Soledad (Rice et al. 1981).
    A group of gray whales known as the Pacific Coast Feeding 
Aggregation (PCFA) feeds along the Pacific coast between southeastern 
Alaska and northern to central California throughout the summer and 
fall (NMFS 2001; Calambokidis et al. 2002; Calambokidis et al. 2004). 
The gray whales in this feeding aggregation are a relatively small 
proportion (a few hundred individuals) of the overall eastern North 
Pacific population and typically arrive and depart from these feeding 
grounds concurrently with the migration to and from the wintering 
grounds (Calambokidis et al. 2002; Allen and Angliss 2010). Although 
some site fidelity is known to occur, there is generally considerable 
inter-annual variation since many individuals do not return to the same 
feeding site in successive years (Calambokidis et al. 2000; 
Calambokidis et al. 2004).
    The Eastern North Pacific stock of gray whale transits through 
Southern California during its northward and southward migrations 
between December and June. Gray whales follow three routes from within 
15 to 200 km from shore (Bonnell and Dailey 1993). The nearshore route 
follows the shoreline between Point Conception and Point Vicente but 
includes a more direct line from Santa Barbara to Ventura and across 
Santa Monica Bay. Around Point Vicente or Point Fermin, some whales 
veer south towards Santa Catalina Island and return to the nearshore 
route near Newport Beach. Others join the inshore route that includes 
the northern chain of the Channel Islands along Santa Cruz Island and 
Anacapa Island and east along the Santa Cruz Basin to Santa Barbara 
Island and the Osborn Bank. From here, gray whales migrate east 
directly to Santa Catalina Island and then to Point Loma or Punta 
Descanso or southeast to San Clemente Island and on to the area near 
Punta Banda. A significant portion of the Eastern North Pacific stock 
passes by San Clemente Island and its associated offshore waters 
(Carretta et al. 2000). The offshore route follows the undersea ridge 
from Santa Rosa Island to the mainland shore of Baja California and 
includes San Nicolas Island and Tanner and Cortes banks (Bonnell and 
Dailey 1993).
    Peak abundance of gray whales off the coast of San Diego is 
typically January during the southward migration and in March during 
the migration north, although females with calves, which depart Mexico 
later than males or females without calves, can be sighted from March 
through May or June (Leatherwood 1974; Poole 1984; Rugh et al. 2001; 
Stevick et al. 2002; Angliss and Outlaw 2008). Gray whales would be 
expected to be infrequent migratory transients within the out portions 
of SSTC only during cold-water months (Carretta et al. 2000). Migrating 
gray whale that might infrequently transit through SSTC would not be 
expected to forage, and would likely be present for minutes to less 
than one or two hours at typical travel speeds of 3 knots 
(approximately 3.5 miles per hour) (Perryman et al. 1999; Mate and 
Urb[aacute]n-Ramirez 2003). A mean group size of 2.9 gray whales was 
reported for both coastal (16 groups) and non-coastal (15 groups) areas 
around San Clemente Island (Carretta et al. 2000). The largest group 
reported was nine animals. The largest group reported by the U.S. Navy 
(1998) was 27 animals. Gray whales would not be expected in the SSTC 
from July through November (Rice et al. 1981), and are excluded from 
warm season analysis. Even though gray whale transitory occurrence is 
infrequent along SSTC, a cold season density is estimated at 0.014 
animals per km\2\ for purposes of conservative analysis.
    Systematic counts of gray whales migrating south along the central 
California coast have been conducted by shore-based observers at 
Granite Canyon most years since 1967. The population size of the 
Eastern North Pacific gray whale stock has been increasing over the 
past several decades at a rate approximately between 2.5 to 3.3% per 
year since 1967. The most recent abundance estimates are based on the 
National Marine Fisheries Service's population estimate of 19,126 
individuals as reported in Allen and Angliss (2010).
    In 1994, due to steady increases in population abundance, the 
Eastern North Pacific stock of gray whales was removed from the List of 
Endangered and Threatened Wildlife, as it was no longer considered 
endangered or threatened under the ESA (Allen and Angliss 2010). The 
Eastern North Pacific stock of gray whale is not considered a strategic 
stock under the MMPA. Even though the stock is within Optimal 
Sustainable Population, abundance will rise and fall as the population 
adjusts to natural and man-caused factors affecting the carrying 
capacity of the environment (Rugh et al. 2005). In fact, it is expected 
that a population close to or at the carrying capacity of the 
environment will be more susceptible to fluctuations in the environment 
(Moore et al. 2001).

Potential Effects on Marine Mammals and Their Habitat

    Anticipated impacts resulting from the Navy's proposed SSTC 
training activities include disturbance from

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underwater detonation events and pile driving from the ELCAS events, if 
marine mammals are in the vicinity of these action areas.

Impacts From Anthropogenic Noise

    Marine mammals exposed to high intensity sound repeatedly or for 
prolonged periods can experience hearing threshold shift (TS), which is 
the loss of hearing sensitivity at certain frequency ranges (Kastak et 
al. 1999; Schlundt et al. 2000; Finneran et al. 2002; 2005). TS can be 
permanent (PTS), in which case the loss of hearing sensitivity is 
unrecoverable, or temporary (TTS), in which case the animal's hearing 
threshold will recover over time (Southall et al. 2007). Since marine 
mammals depend on acoustic cues for vital biological functions, such as 
orientation, communication, finding prey, and avoiding predators, 
marine mammals that suffer from PTS or TTS will have reduced fitness in 
survival and reproduction, either permanently or temporarily. Repeated 
noise exposure that leads to TTS could cause PTS.
    Measured source levels from impact pile driving can be as high as 
214 dB re 1 [mu]Pa @ 1 m. Although no marine mammals have been shown to 
experience TTS or PTS as a result of being exposed to pile driving 
activities, experiments on a bottlenose dolphin (Tursiops truncates) 
and beluga whale (Delphinapterus leucas) showed that exposure to a 
single watergun impulse at a received level of 207 kPa (or 30 psi) 
peak-to-peak (p-p), which is equivalent to 228 dB re 1 [mu]Pa (p-p), 
resulted in a 7 and 6 dB TTS in the beluga whale at 0.4 and 30 kHz, 
respectively. Thresholds returned to within 2 dB of the pre-exposure 
level within 4 minutes of the exposure (Finneran et al. 2002). No TTS 
was observed in the bottlenose dolphin. Although the source level of 
pile driving from one hammer strike is expected to be much lower than 
the single watergun impulse cited here, animals being exposed for a 
prolonged period to repeated hammer strikes could receive more noise 
exposure in terms of SEL than from the single watergun impulse 
(estimated at 188 dB re 1 [mu]Pa\2\-s) in the aforementioned experiment 
(Finneran et al. 2002).
    However, in order for marine mammals to experience TTS or PTS, the 
animals have to be close enough to be exposed to high intensity noise 
levels for prolonged period of time. Current NMFS standards for 
preventing injury from PTS and TTS is to require shutdown or power-down 
of noise sources when a cetacean species is detected within the 
isopleths corresponding to SPL at received levels equal to or higher 
than 180 dB re 1 [mu]Pa (rms), or a pinniped species at 190 dB re 1 
[mu]Pa (rms). Based on the best scientific information available, these 
SPLs are far below the threshold that could cause TTS or the onset of 
PTS. Certain mitigation measures proposed by the Navy, discussed below, 
can effectively prevent the onset of TS in marine mammals, by 
establishing safety zones and monitoring safety zones during the 
training exercise.
    In addition, chronic exposure to excessive, though not high-
intensity, noise could cause masking at particular frequencies for 
marine mammals that utilize sound for vital biological functions. 
Masking can interfere with detection of acoustic signals such as 
communication calls, echolocation sounds, and environmental sounds 
important to marine mammals. Therefore, like TS, marine mammals whose 
acoustical sensors or environment are being masked are also impaired 
from maximizing their performance fitness in survival and reproduction.
    Masking occurs at the frequency band which the animals utilize. 
Therefore, since noise generated from the proposed underwater 
detonation and pile driving and removal is mostly concentrated at low 
frequency ranges, it may have less effect on high frequency 
echolocation sounds by killer whales. However, lower frequency man-made 
noises are more likely to affect detection of communication calls and 
other potentially important natural sounds such as surf and prey noise. 
It may also affect communication signals when they occur near the noise 
band used by the animals and thus reduce the communication space of 
animals (e.g., Clark et al. 2009) and cause increased stress levels 
(e.g., Foote et al. 2004; Holt et al. 2009).
    Masking can potentially impact marine mammals at the individual, 
population, community, or even ecosystem levels (instead of individual 
levels caused by TS). Masking affects both senders and receivers of the 
signals and can potentially have long-term chronic effects on marine 
mammal species and populations in certain situations. Recent science 
suggests that low frequency ambient sound levels have increased by as 
much as 20 dB (more than 3 times in terms of SPL) in the world's ocean 
from pre-industrial periods, and most of these increases are from 
distant shipping (Hildebrand 2009). All anthropogenic noise sources, 
such as those from underwater explosions and pile driving, contribute 
to the elevated ambient noise levels and, thus intensify masking. 
However, single detonations are unlikely to contribute much to masking.
    Since all of the underwater detonation events and ELCAS events are 
planned in a very shallow water situation (wave length >> water depth), 
where low frequency propagation is not efficient, the noise generated 
from these activities is predominantly in the low frequency range and 
is not expected to contribute significantly to increased ocean ambient 
noise.
    Finally, exposure of marine mammals to certain sounds could lead to 
behavioral disturbance (Richardson et al. 1995). Behavioral responses 
to exposure to sound and explosions can range from no observable 
response to panic, flight and possibly more significant responses as 
discussed previously (Richardson et al. 1995; Southall et al. 2007). 
These responses include: changing durations of surfacing and dives, 
number of blows per surfacing, or moving direction and/or speed; 
reduced/increased vocal activities, changing/cessation of certain 
behavioral activities (such as socializing or feeding); visible startle 
response or aggressive behavior (such as tail/fluke slapping or jaw 
clapping), avoidance of areas where noise sources are located, and/or 
flight responses (e.g., pinnipeds flushing into water from haulouts or 
rookeries) (Reviews by Richardson et al. 1995; Wartzok et al. 2003; Cox 
et al. 2006; Nowacek et al. 2007; Southall et al. 2007).
    The biological significance of many of these behavioral 
disturbances is difficult to predict, especially if the detected 
disturbances appear minor. However, the consequences of behavioral 
modification could be expected to be biologically significant if the 
change affects growth, survival, and reproduction. Some of these 
significant behavioral modifications include:
     Drastic change in diving/surfacing patterns (such as those 
thought to be causing beaked whale stranding due to exposure to 
military mid-frequency tactical sonar);
     Habitat abandonment due to loss of desirable acoustic 
environment; and
     Cease feeding or social interaction.
    For example, at the Guerreo Negro Lagoon in Baja California, 
Mexico, which is one of the important breeding grounds for Pacific gray 
whales, shipping and dredging associated with a salt works may have 
induced gray whales to abandon the area through most of the 1960s 
(Bryant et al. 1984). After these activities stopped, the lagoon was 
reoccupied, first by single whales and later by cow-calf pairs.
    The onset of behavioral disturbance from anthropogenic noise 
depends on

[[Page 64284]]

both external factors (characteristics of noise sources and their 
paths) and the receiving animals (hearing, motivation, experience, 
demography) and is also difficult to predict (Southall et al. 2007).
    However, the proposed action area is not believed to be a prime 
habitat for marine mammals, nor is it considered an area frequented by 
marine mammals. Therefore, behavioral disturbances that could result 
from anthropogenic construction noise associated with the Navy's 
proposed training activities are expected to affect only a small number 
of marine mammals on an infrequent basis.

Impacts From Underwater Detonations at Close Range

    In addition to noise induced disturbances and harassment, marine 
mammals could be killed or injured by underwater explosions due to the 
impacts to air cavities, such as the lungs and bubbles in the 
intestines, to the shock wave (Elsayed 1997; Elsayed and Gorbunov 
2007). The criterion for mortality and non-auditory injury used in MMPA 
take authorization is the onset of extensive lung hemorrhage and slight 
lung injury or ear drum rupture, respectively (see Table 3). Extensive 
lung hemorrhage is considered debilitating and potentially fatal as a 
result of air embolism or suffocation. In this Incidental Harassment 
Authorization application, all marine mammals within the calculated 
radius for 1% probability of onset of extensive lung injury (i.e., 
onset of mortality) are counted as lethal exposures. The range at which 
1% probability of onset of extensive lung hemorrhage is expected to 
occur is greater than the ranges at which 50% to 100% lethality would 
occur from closest proximity to the charge or from presence within the 
bulk cavitation region. (The region of bulk cavitation is an area near 
the surface above the detonation point in which the reflected shock 
wave creates a region of cavitation within which smaller animals would 
not be expected to survive). Because the range for onset of extensive 
lung hemorrhage for smaller animals exceeds the range for bulk 
cavitation and all more serious injuries, all smaller animals within 
the region of cavitation and all animals (regardless of body mass) with 
more serious injuries than onset of extensive lung hemorrhage are 
accounted for in the lethal exposures estimate. The calculated maximum 
ranges for onset of extensive lung hemorrhage depend upon animal body 
mass, with smaller animals having the greatest potential for impact, as 
well as water column temperature and density.
    However, due to the small detonation that would be used in the 
proposed SSTC training activities and the resulting small safety zones 
to be monitored and mitigated for marine mammals in the vicinity of the 
proposed action area, it is unlikely that marine mammals would be 
killed or injured by underwater detonations.

Impact Criteria and Thresholds

    The effects of an at-sea explosion or pile driving on a marine 
mammal depends on many factors, including the size, type, and depth of 
both the animal and the explosive charge/pile being driven; the depth 
of the water column; the standoff distance between the charge/pile and 
the animal; and the sound propagation properties of the environment. 
Potential impacts can range from brief acoustic effects (such as 
behavioral disturbance), tactile perception, physical discomfort, 
slight injury of the internal organs and the auditory system, to death 
of the animal (Yelverton et al. 1973; O'Keeffe and Young 1984; DoN 
2001). Non-lethal injury includes slight injury to internal organs and 
the auditory system; however, delayed lethality can be a result of 
individual or cumulative sub-lethal injuries (DoN 2001). Short-term or 
immediate lethal injury would result from massive combined trauma to 
internal organs as a direct result of proximity to the point of 
detonation or pile driving (DoN 2001).
    This section summarizes the marine mammal impact criteria used for 
the subsequent modeled calculations. Several standard acoustic metrics 
(Urick 1983) are used to describe the thresholds for predicting 
potential physical impacts from underwater pressure waves:
     Total energy flux density or Sound Exposure Level (SEL). 
For plane waves (as assumed here), SEL is the time integral of the 
instantaneous intensity, where the instantaneous intensity is defined 
as the squared acoustic pressure divided by the characteristic 
impedance of sea water. Thus, SEL is the instantaneous pressure 
amplitude squared, summed over the duration of the signal and has dB 
units referenced to 1 re [micro]Pa\2\-s.
     \1/3\-octave SEL. This is the SEL in a \1/3\-octave 
frequency band. A \1/3\-octave band has upper and lower frequency 
limits with a ratio of 21:3, creating bandwidth limits of about 23 
percent of center frequency.
     Positive impulse. This is the time integral of the initial 
positive pressure pulse of an explosion or explosive-like wave form. 
Standard units are Pa-s, but psi-ms also are used.
     Peak pressure. This is the maximum positive amplitude of a 
pressure wave, dependent on charge mass and range. Units used here are 
psi, but other units of pressure, such as [micro]Pa and Bar, also are 
used.
1. Harassment Threshold for Sequential Underwater Detonations
    There may be rare occasions when sequential underwater detonations 
are part of a static location event. Sequential detonations are more 
than one detonation within a 24-hour period in a geographic location 
where harassment zones overlap. For sequential underwater detonations, 
accumulated energy over the entire training time is the natural 
extension for energy thresholds since energy accumulates with each 
subsequent shot.
    For sequential underwater detonations, the acoustic criterion for 
behavioral harassment is used to account for behavioral effects 
significant enough to be judged as harassment, but occurring at lower 
sound energy levels than those that may cause TTS. The behavioral 
harassment threshold is based on recent guidance from NMFS (NMFS 2009a; 
2009b) for the energy-based TTS threshold. The research on pure tone 
exposures reported in Schlundt et al. (2000) and Finneran and Schlundt 
(2