Takes of Marine Mammals Incidental to Specified Activities; Construction of the Parsons Slough Sill Project, 61432-61440 [2010-24986]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 75, Number 192 (Tuesday, October 5, 2010)]
[Notices]
[Pages 61432-61440]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-24986]


-----------------------------------------------------------------------

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XY30


Takes of Marine Mammals Incidental to Specified Activities; 
Construction of the Parsons Slough Sill Project

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

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

-----------------------------------------------------------------------

SUMMARY: NMFS has received an application from the NOAA Restoration 
Center, Southwest Region, for an Incidental Harassment Authorization 
(IHA) to take marine mammals, by harassment, incidental to the Parsons 
Slough Sill Project. Pursuant to the Marine Mammal Protection Act 
(MMPA), NMFS is requesting comments on its proposal to issue an IHA to 
the NOAA Restoration Center, Southwest Region, to take, by Level B 
Harassment only, small numbers of harbor seals (Phoca vitulina 
richardsi) during the specified activity.

DATES: Comments and information must be received no later than November 
4, 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. The mailbox address for providing e-
mail comments is PR1.0648-XY30@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: Brian D. Hopper or Candace Nachman, 
Office of Protected Resources, NMFS, (301) 713-2289, or Monica 
DeAngelis, NMFS Southwest Region, (562) 980-3232.

SUPPLEMENTARY INFORMATION:

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce to allow, upon request, the 
incidental, but not intentional, taking of small numbers of marine 
mammals by U.S. citizens who engage in a specified activity (other than 
commercial fishing) within a specified geographical region if certain 
findings are made and either regulations are issued or, if the taking 
is limited to harassment, a notice of a proposed authorization is 
provided to the public for review.
    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 takings 
are set forth. NMFS has defined ``negligible impact'' in 50 CFR 216.103 
as ``* * * an impact resulting from the specified activity that cannot 
be reasonably expected to, and is not reasonably likely to, adversely 
affect the species or stock through effects on annual rates of 
recruitment or survival.''
    Section 101(a)(5)(D) of the MMPA established an expedited process 
by which citizens of the U.S. 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 authorization published in the Federal Register for the 
incidental harassment of marine mammals. Within 45 days of the

[[Page 61433]]

close of the comment period, NMFS must either issue or deny the 
authorization.
    Except with respect to certain activities not pertinent here, the 
MMPA defines ``harassment'' as:

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

Summary of Request

    NMFS received an application on August 5, 2010, from the NOAA 
Restoration Center, Southwest Region, for the taking, by harassment, of 
marine mammals incidental to the construction of a partially submerged 
tidal barrier (sill) across the mouth of the Parsons Slough Channel. 
Parsons Slough is located on the southeast side of the Elkhorn Slough 
Estuary, which is situated 90 miles (145 km) south of San Francisco and 
20 miles (32 km) north of Monterey in Monterey County, California. The 
application was determined to be complete on August 16, 2010. The sill 
structure would be constructed of steel sheet piles and would extend 
270 ft (82.3 m) across the mouth of Parsons Slough. The sheet pile wall 
would be supported on two rows of seven end-bearing piles. All sheet 
pile and end-bearing piles would be driven starting with a vibratory 
hammer to set the sheets but may require an impact hammer to complete 
driving. Because pile driving has the potential to expose marine 
mammals to heightened levels of underwater and ambient noise, it may 
result in behavioral harassment to marine mammals located in the action 
area. An authorization under section 101(a)(5)(D) of the MMPA is 
required. The proposed action will result in the incidental take, by 
Level B harassment, of Pacific harbor seals (Phoca vitulina richarsi). 
The specified activities are also likely to result in the take by 
incidental harassment of southern sea otters (Enhydra lutirs). The U.S. 
Fish and Wildlife Service (USFWS) has management jurisdiction over 
southern sea otters. NOAA has applied for and received from USFWS a 
separate MMPA Section 101(a)(5)(D) authorization for incidental take of 
sea otters. The potential take of sea otters is not further addressed 
in this notice.

Description of the Specified Activity

    The proposed sill structure would be located in the vicinity of the 
Union Pacific Railroad bride, milepost 103.27 Coast Subdivision, which 
is located at the mouth of the Parsons Slough Complex. The bridge is a 
165 ft (50.3 m) long concrete slab girder bridge that spans the Parsons 
Slough Channel. The overall goal of the proposed action is to reduce 
tidal scour within the Elkhorn Slough action area in general and the 
Parsons Slough study area in particular. Within the past 60 years, the 
proportion of salt marsh habitat and mudflat habitat within the Elkhorn 
Slough has reversed as a result of tidal erosion and inundation of 
interior marsh areas. Currently, there are approximately 800 acres (3.2 
km\2\) of salt marsh and tidal creeks within Elkhorn Slough, 1,600 
acres (6.5 km\2\) of mudflat, and 300 acres (1.2 km\2\) of tidal 
channels. Modeling efforts predict that an additional 550 acres (2.2 
km\2\) of salt marsh would be lost over the next 50 years if tidal 
erosion in Elkhorn Slough is not addressed. Without intervention, 
excessive erosion would continue to widen tidal channels and convert 
salt marsh to mud flat. This would result in a significant loss of 
habitat function and a decrease in estuarine biodiversity.
    In order to reduce tidal scour, the NOAA Restoration Center, 
Southwest Region, proposes to construct a partially submerged tidal 
barrier (sill), similar to an underwater wall, across the mouth of 
Parsons Slough. The sill structure would prevent head cutting (i.e., 
erosion in a channel caused by an abrupt change in slope) in Elkhorn 
Slough from migrating upstream into Parsons Slough, would retain 
sediment that accretes within Parsons Slough, and would reduce the 
tidal prism of Parsons Slough. This reduction in tidal prism would 
reduce current velocities between Parsons Slough and the mouth of 
Elkhorn Slough, thereby reducing tidal scour. The proposed project, 
which is referred to as the Parsons Slough Project, would also include 
establishment of artificial reefs to support populations of Olympia 
oysters (Ostrea lurida) in the northeastern part of the Parsons Slough 
Complex.
    As mentioned earlier in this document, the sill structure would be 
constructed of steel sheet piles that would extend 270 ft (82.3 m) 
across the mouth of the Parsons Slough Channel. A 100 ft (30 m) wide 
lower area, located in the center of the structure, would allow water 
to flow between Parsons Slough and Elkhorn Slough. This portion of the 
structure would be submerged more than 99 percent of the time. The 
center of the lower part of the structure would include a notch 
approximately 25 ft (7.6 m) wide, with the top elevation of the sheet 
pile in this notch at an elevation of -5 ft (-1.5 m). The notch would 
provide for the passage of water at all tide levels and would 
facilitate the movement of fish and wildlife into and out of Parsons 
Slough. The top elevation of the sheet pile in the remaining 75 ft (23 
m) of the central section of the base structure would be -2 ft (-0.6 
m). The remaining portions of the sheet piles to the left and right of 
the center portion of the structure would have a top elevation of 9.6 
ft (3 m).
    All in-channel construction activities would be constructed from 
barges, and no heavy equipment would enter the channels. Most of these 
construction activities are in-water (e.g., installation of end-bearing 
piles and sheet piles, placement of rockfill buttress).
    Installation of the sheet pile wall would be supported by two rows 
of seven end-bearing piles, as well as a single row of sheet pile 
located between the piles. The end-bearing piles would be driven 
through the soft soils to penetrate 10 ft (3 m) below the top of the 
dense sandy deposits that underlie the soft soils at an elevation of 
approximately -80 ft (-24.4 m). Additionally, up to 45 temporary end-
bearing piles may be installed in the main channel of Elkhorn Slough at 
the Kirby Park staging site (approximately 2 mi (3.2 km) from the 
project site) to facilitate barge docking and loading (if the temporary 
dock is constructed on pilings, rather than temporary rock-fill). These 
piles, if necessary, would be removed after construction when the 
floating dock is disassembled. Pile driving at the staging site is not 
expected to result in any harbor seal takes. Harbor seals usually occur 
just beyond the mouth of Elkhorn Slough in the Moss Landing harbor and 
in the Salinas River channel south of the Moss Landing Bridge, and the 
lower portion of Elkhorn Slough extending up to Parsons Slough and 
Rubis Creek. Harbor seals do not typically use the part of the estuary 
that leads up to Kirby Creek and the nearest occupied areas and haul-
out locations (approximately 2 mi (3.2 km) to the south) are beyond the 
estimated distances to NMFS' current threshold sound levels from pile 
driving proposed at the Kirby Park staging area (see Table 3 and Table 
4).
    A vibratory hammer would be used to start driving all sheet pile 
and end-bearing piles, but an impact hammer may be required to complete 
driving. If an impact hammer is required during construction, 
cushioning blocks would be used to attenuate the sound. Vibratory 
hammers clamp onto the sheet pile, therefore, no cushioning blocks

[[Page 61434]]

would be used during vibratory pile driving.

       Table 1--Typical Near-Source (10m) Underwater Noise Levels
------------------------------------------------------------------------
        Type of pile            Driving technique         RMS level
------------------------------------------------------------------------
H-Pile......................  Impact Hammer.......  183 dB
H-Pile......................  Vibratory Hammer....  155 dB
Sheet Pile..................  Impact Hammer.......  175 dB
Sheet Pile..................  Vibratory Hammer....  160 dB
------------------------------------------------------------------------


                  Table 2--Airborne Noise Nevel (15 m)
------------------------------------------------------------------------
        Type of pile            Driving technique      Lmax/rms level
------------------------------------------------------------------------
H-Pile......................  Impact Hammer.......  109 dBA
H-Pile......................  Vibratory Hammer....  95 dBA
Sheet Pile..................  Impact Hammer.......  106 dBA
Sheet Pile..................  Vibratory Hammer....  97 dBA
------------------------------------------------------------------------

    The applicant anticipates that construction would last 11 to 15 
weeks beginning around November 1, 2010 and ending in February 2011. 
In-water construction would primarily occur during slack tide. Actual 
pile driving time during this work window will depend on a number of 
factors, such as sediments, currents, presence of marine mammals, and 
equipment maintenance; however, the applicant anticipates that it will 
take approximately 20 days to install the end-bearing piles and sheet 
pile during the 11 to 15 weeks of construction. Construction activities 
at night are also anticipated during this 11 to 15 week period but 
would not last for more than 5 hrs at a time (duration of a slack tide 
at night).

Description of Marine Mammals in the Area of the Specified Activity

    Two species of marine mammals may be affected by the proposed 
action: Pacific harbor seals and southern sea otters (Enhydra lutirs). 
However, southern sea otters are managed by the U.S. Fish and Wildlife 
Service and will not be considered further in this proposed IHA notice.

Pacific Harbor Seals

    Harbor seals are the most widely distributed pinniped species, 
occurring on both sides of the northern Pacific and Atlantic Oceans 
(NMFS, 2005). The Pacific harbor seal ranges from Baja Mexico to the 
Aleutian Islands and occurs along the entire length of the California 
coast. In 2005, harbor seal populations in California were estimated at 
34,233 and have been growing at an estimated rate of 3.5 percent from 
1982 to 1995 (NMFS, 2005). Harbor seals are not listed as depleted 
under the MMPA or threatened or endangered under the Endangered Species 
Act (ESA).
    The harbor seal breeding season lasts from March through June each 
year, with peak births occurring between April and May. Females give 
birth to one pup each year and mate again shortly after weaning. Harbor 
seals are not territorial on land but they do maintain spacing between 
individuals in haul outs.
    Harbor seals feed on fish, crustaceans, and some cephalopods. 
Foraging occurs in shallow littoral waters, and common prey items 
include flounder, sole, hake, codfish, sculpin, anchovy, and herring. 
Harbor seals are typically solitary while foraging, although small 
groups have been observed.
    Harbor seals are rarely found in pelagic waters and typically stay 
within the tidal and intertidal zones. On land, harbor seals haul out 
on rocky outcrops, mudflats, sandbars, and sandy beaches with 
unrestricted access to water and with minimal human presence. Harbor 
seals are non-migratory, but will make short to moderate distance 
journeys for feeding and breeding, including venturing into estuaries 
and rivers (CDFG, 2005).
    Harbor seals use Elkhorn Slough for hauling out, resting, 
socializing, foraging, molting, and reproduction. Within the Parsons 
Slough Complex, there are an estimated 100 harbor seals using the area 
on a daily basis (Maldini et al., 2009). In Parsons Slough, harbor 
seals use exposed mudflats to haul-out during low tide. During high 
tide, harbor seals are absent from Parsons Slough (Maldini et al., 
2009). There are five main haul-out areas within the Parsons Slough 
Complex, two of which are located east and west of the Union Pacific 
Railroad bridge, respectively (Maldini et al., 2009). Consistent with 
harbor seal behavior, abundance on the mudflats is highest during the 
day and drops after sunset. Harbor seal activity at night is unknown, 
but researchers speculate that the animals leave Parsons Slough at 
night to forage in the main channel or Monterey Bay (Maldini et al., 
2009). Maldini et al. (2009) found that exit times peaked at 5 pm and 
continued to be high until 8 pm with another smaller peak occurring 
around 10 pm. Additional information on the Pacific harbor seal can be 
found in the NMFS Stock Assessment Report (SAR). The 2009 Pacific SAR 
is available at https://www.nmfs.noaa.gov/pr/pdfs/sars/po2009.pdf.

Potential Effects of the Specified Activity on Marine Mammals

    Sound is a physical phenomenon consisting of minute vibrations that 
travel through a medium, such as air or water. Sound levels are 
compared to a reference sound pressure to identify the medium. For air 
and water, these reference pressures are ``re 20 microPa'' and ``re 1 
microPa,'' respectively. Sound is generally characterized by several 
variables, including frequency and sound level. Frequency describes the 
sound's pitch and is measured in hertz (Hz) or kilohertz (kHz), while 
sound level describes the sound's loudness and is measured in decibels 
(dB). Sound level increases or decreases exponentially with each dB of 
change. For example, 10-dB yields a sound level 10 times more intense 
than 1 dB, while a 20 dB level equates to 100 times more intense, and a 
30 dB level is 1,000 times more intense. However, it should be noted 
that humans perceive a 10 dB increase in sound level as only a doubling 
of sound loudness, and a 10 dB decrease in sound level as a halving of 
sound loudness.

[[Page 61435]]

    Marine mammals use sound for vital life functions, and introducing 
sound into their environment could disrupt those behaviors. Sound 
(hearing and vocalization) serves four main functions for marine 
mammals. These functions include: (1) Providing information about their 
environment; (2) communication; (3) enabling remote detection of prey; 
and (4) enabling detection of predators. Noise from pile driving may 
affect marine mammals at a level which could cause Level B behavioral 
harassment by disturbing important behavioral patterns of Pacific 
harbor seals. The distances at which these sounds may be audible depend 
on the source levels, ambient noise levels, and sensitivity of the 
receptor (Richardson et al., 1995). Mitigation measures (see Proposed 
Mitigation section later in this document) and the low source level of 
vibratory pile driving (the main method used to install sheet pile and 
end-bearing piles in this proposed project) are expected to prevent 
marine mammals from being exposed to injurious levels of sound.
    Pinnipeds produce a wide range of social signals, most occurring at 
relatively low frequencies (Southall et al., 2007), suggesting hearing 
is keenest at these frequencies. Pinnipeds communicate acoustically 
both on land and in the water, suggesting that they possess amphibious 
hearing and have different hearing capabilities dependent upon the 
media (air or water). Based on numerous studies, as summarized in 
Southall et al. (2007), pinnipeds are more sensitive to a broader range 
of sound frequencies in water than in air. In-water, pinnipeds can hear 
frequencies from 75 Hz to 75 kHz. In air, the lower limit remains at 75 
Hz, but the highest audible frequencies are only around 30 kHz 
(Southall et al., 2007).

Hearing Impairment

    Temporary or permanent hearing impairment is possible when marine 
mammals are exposed to very loud sounds. Hearing impairment is measured 
in two forms: Temporary threshold shift (TTS) and permanent threshold 
shift (PTS). Relationships between TTS and PTS have not been studied in 
marine mammals, but are assumed to be similar to those in humans and 
terrestrial mammals. There is no empirical data for onset of PTS in any 
marine mammal, therefore, PTS-onset must be estimated from TTS-onset 
measurements and from the rate of TTS growth with increasing exposure 
levels above those eliciting TTS-onset. NMFS presumes PTS to be likely 
if the threshold is reduced by >= 40 dB (i.e., 40 dB of TTS). Due to 
proposed mitigation measures and the fact that source levels of the 
impact and vibratory hammers are below the 190 dB injury threshold used 
by NMFS for pinniped species, NMFS does not expect that harbor seals 
will be exposed to levels that could elicit PTS; therefore, it will not 
be discussed further.

Temporary Threshold Shift (TTS)

    TTS is the mildest form of hearing impairment that can occur during 
exposure to a loud sound (Kryter, 1985). While experiencing TTS, the 
hearing threshold rises, and a sound must be louder in order to be 
heard. TTS can last from minutes or hours to (in cases of strong TTS) 
days. For sound exposures at or somewhat above the TTS-onset threshold, 
hearing sensitivity recovers rapidly after exposure to the noise ends. 
Few data on sound levels and durations necessary to elicit mild TTS 
have been obtained for marine mammals. Southall et al. (2007) considers 
a 6 dB TTS (i.e., baseline thresholds are elevated by 6 dB) sufficient 
to be recognized as an unequivocal deviation and thus a sufficient 
definition of TTS-onset. Because it is non-injurious, NMFS considers 
TTS to be Level B harassment that is mediated by physiological effects 
on the auditory system; however, NMFS does not consider onset TTS to be 
the lowest level at which Level B harassment may occur.
    Sound exposures that elicit TTS in pinnipeds underwater have been 
measured in harbor seals, California sea lions, and northern elephant 
seals from broadband or octaveband (OBN) non-pulse noise ranging from 
approximately 12 minutes to several hours (Kastak and Schusterman, 
1996; Finneran et al., 2003; Kastak et al., 1999; Kastak et al., 2005). 
Collectively, Kastak et al. (2005) analyzed these data to indicate that 
in the harbor seal a TTS of ca. 6 dB occurred with 25 minute exposure 
to 2.5 kHz OBN with sound pressure level (SPL) of 152 dB re 1 microPa 
(as summarized in Southall et al., 2007). Underwater TTS experiments 
involving exposure to pulse noise are limited to a single study. 
Finneran et al. (2003) found no measurable TTS when two California sea 
lions were exposed to sounds up to 183 dB re 1 microPa (peak-to-peak).

Behavioral Impacts

    The source of underwater noise during construction would be pile 
driving to install the end-bearing piles and sheet pile tidal barrier. 
There are limited data available on the effects of non-pulse noise on 
pinnipeds in-water; however, field and captive studies to date 
collectively suggest that pinnipeds do not strongly react to exposure 
between 90-140 dB re 1 microPa. Jacobs and Terhune (2002) observed wild 
harbor seal reactions to acoustic harassment devices (AHDs) around nine 
sites. Seals came within 144.4 ft (44 m) of the active AHD and failed 
to demonstrate any behavioral response when received SPLs were 
estimated at 120-130 dB re 1 microPa. In a captive study, a group of 
seals were collectively subjected to non-pulse sounds (e.g., vibratory 
pile driving) at 8-16 kHz (Kastelein, 2006). Exposures between 80-107 
dB re 1 microPa did not induce strong behavioral responses; however, a 
single observation at 100-110 dB re 1 microPa indicated an avoidance 
response at this level. The group returned to baseline conditions 
following exposure (i.e., no long term impact). Southall et al. (2007) 
notes contextual differences between these two studies, noting that the 
captive animals were not reinforced with food for remaining in the 
noise fields, whereas free-ranging subjects may have been more tolerant 
of exposures because of motivation to return to a safe location or 
approach enclosures holding prey items. Southall et al. (2007) reviewed 
relevant data from studies involving pinnipeds exposed to pulse noise 
(e.g., impact pile driving) and concluded that exposures of 150 to 180 
dB re 1 microPa generally have limited potential to induce avoidance 
behavior.
    Seals exposed to sound levels that exceed the Level B harassment 
threshold (120 dB for non-pulse; 160 dB for pulse) may exhibit 
temporary avoid behavior around the Union Pacific Railroad bridge, 
which may affect movement of seals under the bridge or inhibit them 
from resting at haul-out sites near the bridge. The estimated 11-15 
weeks required for construction may result in the temporary abandonment 
of haul-out sites near the bridge and within Parsons Slough. Although 
harbor seals may temporarily abandon haul out sites, there are an 
abundance of other haul-out sites in the area. Additionally, the 
required mitigation measures restrict construction to the non-breeding 
season to avoid impacts to potentially sensitive mother-pup pairs. In 
general, ambient noise levels in the area are low; however, animals in 
the vicinity of the project site have been exposed to various types and 
levels of anthropogenic noise--from recreational boating, to the 15-20 
trains that pass daily over the Union Pacific Railroad bridge. Harbor 
seals have also been exposed to in-water construction activities at the 
site and animals are likely tolerant or habituated to

[[Page 61436]]

anthropogenic disturbance, including pile driving. For example, in 
October 2002, the Union Pacific Railroad replaced the existing wooden 
pile trestle bridge spanning the Parsons Slough Channel with a 165 ft 
(50.3 m) slab girder bridge. Biological monitors reported that harbor 
seals were present during construction and came and went from the site 
without any visible signs of stress or undue harassment (MACTEC 
Engineering and Consulting, 2003).
    Based on these studies and monitoring reports, NMFS has 
preliminarily determined that harbor seals exposed to sound levels 
exceeding the Level B harassment threshold (120 dB for non-pulse; 160 
dB for pulse) may exhibit temporary avoidance behavior. The most likely 
impact to harbor seals from the sheet pile and end-bearing pile 
installation would be temporary disruption of resting patterns because 
individual harbor seals may abandon haul out sites and leave the area 
during construction activities. However, the scheduling of construction 
activities during the non-breeding season will avoid more severe 
effects such as reduced pup survival due to mother-pup separation and 
interrupted suckling bouts. Temporary hearing loss is unlikely for 
those harbor seals that enter into the zone of Level B harassment 
because source levels from vibratory pile driving are not loud enough 
to induce TTS. Furthermore, the short duration of impact pile driving 
and close proximity to the source necessary to induce TTS makes it 
unlikely that harbor seals would be exposed to source levels loud 
enough to induce TTS. Permanent hearing loss or other harm is not 
anticipated due to monitoring and mitigation efforts (described below) 
and the low source levels of pile driving hammers to be used in this 
proposed project; however, even without mitigation measures, it is 
unlikely that harbor seals would experience Level A harassment, serious 
injury or mortality because of the close proximity to the source 
necessary to induce these types of impacts and the avoidance behavior 
expected of harbor seals during pile driving activities.

Anticipated Effects on Habitat

    The proposed action requires the placement of about 2,000 yd\3\ 
(1,529 m\3\) of fill (rock and sheet pile), which would result in the 
permanent loss of approximately 0.75 acres (3,035 m\2\) of subtidal 
habitat within the project footprint. The expected extent of direct 
habitat loss is equivalent to approximately 2.3 percent of the subtidal 
habitat area (32.9 acres (0.13 km\2\)) present within Parsons Slough, 
and a fraction of the subtidal habitat within Elkhorn Slough (1,400 
acres (5.7 km\2\)). Although the proposed action would permanently 
alter habitat within the project footprint, harbor seals haul-out in 
many locations throughout the estuary, and the proposed action is not 
expected to have any habitat-related effects that could cause 
significant or long-term consequences for individual harbor seals or 
their population.
    Long-term operation of the proposed sill is expected to result in 
the conversion of approximately 11 acres (0.04 km\2\) of intertidal 
mudflat habitat to subtidal habitat. The conversion of intertidal 
habitat to subtidal habitat will have no adverse effect and possibly a 
long-term beneficial effect on harbor seals by improving ecological 
function of the slough, such as higher species diversity, more species 
abundance, larger fish, and better habitat. Moreover, decrease of 
mudflat by up to 11 acres (0.04 km\2\) would not cause significant or 
long-term consequences for individual harbor seals or their population 
because harbor seals typically use a very small percentage of the 
potential haul-out sites that currently exist throughout the slough 
complex. Therefore, the proposed activity is not expected to have any 
habitat-related effects that could cause significant or long-term 
consequences for individual harbor seals or their population.
    It is unlikely that the sill structure itself, when completed, will 
result in long-term adverse effects on harbor seal movements through 
the slough because the sill structure allows for continued access to 
Parsons Slough by aquatic species, including harbor seals. A 25 ft (7.6 
m) long section of the sill will be completely underwater with a 
minimum of 5 ft (1.5 m) of water above it at all times. On either side 
of this 25 ft (7.6 m) section will be two 37 ft (11.3 m) sections that 
will be under 2 ft (.6 m) of water. The remaining 170 ft (51.8 m) of 
the sill structure will be above water. With respect to increased 
velocities, the current velocity of water flowing under the bridge is 
5.6 ft (1.7 m) per second during ebbing tides and 4.9 ft (1.5 m) per 
second during flood tides (Moffat and Nichol, 2008). When completed, 
the sill structure will increase current velocities in the vicinity of 
the structure. The greatest turbulence would be during spring tides 
near low tide. For example, the applicant's modeling results indicate 
that peak velocities at the sill during spring ebb tide would not 
exceed 10.7 ft (3.3 m) per second, which is much slower than the 
average wave velocities in Monterey Bay that harbor seals easily 
navigate on a daily basis. At -5 ft (-1.5 m) elevation, where 
velocities are anticipated to be higher, velocities on an ebb tide 
would be less than 5.6 ft (1.7 m) per second approximately 90 percent 
of the time; velocities would never exceed about 4.5 ft (1.4 m) per 
second on a flood tide. The sill structure would not alter velocities 
during slack tide; therefore, conditions at optimal movement times 
would not change from the baseline conditions. During times of high 
velocity, the seals may avoid crossing the sill structure. The 
exception to this may be inexperienced mothers with young pups that 
could get swept into Parsons Slough. This would not injure pups, but it 
may result in pups staying in Parsons Slough longer than they would 
otherwise. Therefore, the proposed activity is not expected to have any 
habitat-related effects that could cause significant or long-term 
consequences for individual harbor seals or their population.
    Harbor seals and forage fish may occupy the same habitat and harbor 
seal distributions within the estuary reflect foraging locations to 
some extent. Noise from pile driving would result in degradation of in-
water habitat; however, this impact would be short term and site-
specific, and habitat conditions would return to their pre-disturbance 
state shortly after the cessation of in-water construction activities. 
In addition, research by Oxman (1995) and Harvey et al. (1995) 
comparing catch rates from trawls conducted in the Slough to species 
detected in seal scat found that seals primarily feed between Seal Bend 
and the oceanic nearshore shelf in Monterey Bay. Oxman (1995) also 
radio-tagged seals and found that they all spend their nights diving 
within 0.5 to 7 km of shore, most (88 percent) 1.25 km south of the 
Slough entrance, with the others (12 percent) either 4 km north at the 
Pajaro Rivermouth, or 7.25 km north at Sunset Beach, Santa Cruz. 
Therefore, because any habitat disturbance caused by pile driving will 
be short-term and site specific, and in light of the fact that harbor 
seals may conduct most foraging in the nearshore oceanic and not at the 
project site, NMFS does not expect the proposed action to have habitat-
related effects on either forage fish populations or harbor seal 
foraging success that could cause long-term consequences for individual 
harbor seals or their population.

Proposed Mitigation

    In order to issue an incidental take authorization (ITA) under 
Section 101(a)(5)(D) of the MMPA, NMFS mustset forth the permissible 
methods

[[Page 61437]]

of taking pursuant to such activity, and other means of effecting the 
least practicable impact on such species or stock and its habitat, 
paying particular attention to rookeries, mating grounds, and areas of 
similar significance, and on the availability of such species or stock 
for taking for certain subsistence uses (where relevant).
    The applicant has proposed mitigation measures in their application 
for reducing impacts to environmental resources. For example, 
installing end-bearing piles and sheet pile with a vibratory hammer 
instead of an impact hammer will introduce less sound into the marine 
environment and prevent marine mammals from being exposed to injurious 
levels of sound. Some of the following proposed mitigation measures 
that follow were developed by the NOAA Restoration Center, Southwest 
Region and accepted by NMFS while others were developed in discussions 
between the applicant and NMFS' Office of Protected Resources. These 
proposed mitigation measures are designed to eliminate the potential 
for injury and reduce Level B harassment of marine mammals.

Establishment of Safety Zones and Shut Down Requirements

    Vibratory pile driving does not result in source levels that are at 
or above NMFS' harassment threshold for Level A harassment; therefore, 
shut down zones would not be required for vibratory pile driving. For 
impact pile driving, the isolpleth for the Level A harassment threshold 
(190 dB re 1 microPa rms) is modeled to be within 10 ft (3 m) of end-
bearing piles driven with a impact hammer and 5 ft (1.5 m) of sheet 
piles driven with an impact hammer; The NOAA Restoration Center, 
Southwest Region, and NMFS, however, have proposed to delay impact pile 
driving if a harbor seal comes within 33 ft (10 m) of the pile being 
driven, which further reduces the risk of Level A harassment. In 
addition, if an impact hammer is required during construction, 
cushioning blocks would be used to help attenuate the sound.

Construction Timing

    Pile driving is anticipated to occur during an 11 to 15 week period 
beginning around November 1, 2010 and ending in February 2011. This 
work window was selected to coincide with the non-pupping season for 
harbor seals and avoid haul-out site abandonment during pupping season 
that may result in reduced pup survival due to mother/pup separation 
and interrupted suckling bouts. The work window also coincides with the 
U.S. Fish and Wildlife Department's required construction work window 
to avoid the peak pupping period for sea otters (75 FR 42121, July 20, 
2010). In addition, in-water construction activities such as pile 
driving will be conducted during high tide when haul-out sites are 
inaccessible, and harbor seals are largely absent from Parsons Slough 
(Maldini et al., 2009).

Limited Use of Impact Hammer

    All piles would be installed using a vibratory pile driver unless 
sufficient depth cannot be reached, at which point an impact hammer may 
be used. If an impact hammer is required, cushioning blocks would be 
used as an attenuation device to reduce hydroacoustic sound levels and 
avoid the potential for injury. These actions would also serve to 
reduce impacts to harbor seals.

Mitigation Monitoring

    Monitoring during construction of the sill would occur from an 
observation post adjacent to the Union Pacific railroad bridge as well 
as from a zodiac. Monitoring would be conducted by qualified, NMFS 
approved protected species observers (PSOs). On a daily basis, 
construction monitoring would begin 30 minutes prior to the initiation 
of construction activities and continue until 30 minutes after 
construction activities have ceased for the day. The PSO would maintain 
a log that documents numbers of marine mammals present before, during, 
and at the end of daily construction activities. In addition, the PSO 
would record basic weather conditions (ambient temperature, tidal 
activity, precipitation, wind, horizontal visibility, etc.), as well as 
marine mammal behavior.
    The PSO would have the authority to cease construction if a harbor 
seal is detected within or approaching the safety zone or if an animal 
appears injured. Within 30 days of the completion of the sill 
construction, a report would be completed and submitted to NMFS that 
would include a summary of the daily log maintained by the PSO during 
construction. In addition, the report would include an assessment of 
the number of harbor seals that may have been harassed as a result of 
pile driving activities, based on direct observation of harbor seals 
observed in the area.

Soft Start to Pile Driving Activities

    A ``soft start'' technique would be used at the beginning of each 
pile installation to allow any harbor seals that may be in the 
immediate area to leave before the activity reaches its full energy. 
The soft start requires contractors to initiate pile driving with a 
vibratory hammer for 15 seconds at reduced energy followed by a 1-
minute waiting period. This procedure would be repeated two additional 
times. Due to the short duration of impact pile driving (typically 
lasting between 1 and 10 minutes), the traditional ramp-up requirement 
does not apply because it would actually increase the duration of noise 
emitted into the environment, and monitoring should effectively detect 
harbor seals within or near the proposed impact pile driving shut down 
zone. If any harbor seals are sighted within or approaching the 33 ft 
(10 m) shut down zone prior to pile driving, the construction 
contractor will delay pile-driving until the animal has moved outside 
and is on a path away from the safety zone or after 15 minutes have 
elapsed since the last sighting.
    NMFS has carefully evaluated the applicant's proposed mitigation 
measures. NMFS accepted some of the applicant's proposed measures, such 
as the seasonal timing of construction, suggested additional mitigation 
measures like the establishment of a 33 ft (10 m) safety zone and 
hydroacoutic monitoring to measure sound pressure levels from pile 
driving, and considered a range of other measures in the context of 
ensuring that NMFS prescribes the means of effecting the least 
practicable impact on the affected marine mammal species and stocks and 
their habitat. Our evaluation of potential measures included 
consideration of the following factors in relation to one another: (1) 
The manner in which, and the degree to which, the successful 
implementation of the measure is expected to minimize adverse impacts 
to marine mammals; (2) the proven or likely efficacy of the specific 
measure to minimize adverse impacts as planned; and (3) the 
practicability of the measure for applicant implementation, including 
consideration of personal safety, and practicality of implementation.
    Based on our evaluation of the applicant's proposed measures, as 
well as other measures developed by NMFS in cooperation with the 
applicant, NMFS has preliminarily determined that the proposed 
mitigation measures provide the means of effecting the least 
practicable impact on marine mammal species or stocks and their 
habitat, paying particular attention to rookeries, mating grounds, and 
areas of similar significance.

Proposed Monitoring and Reporting

    In order to issue an ITA for an activity, Section 101(a)(5)(D) of 
the MMPA states that NMFS must, where

[[Page 61438]]

applicable, set forth ``requirements pertaining to the monitoring and 
reporting of such taking''. The MMPA implementing regulations at 50 CFR 
216.104(a)(13) indicate that requests for ITAs must include the 
suggested means of accomplishing the necessary monitoring and reporting 
that will result in increased knowledge of the species and of the level 
of taking or impacts on populations of marine mammals that are expected 
to be present in the proposed action area.
    Monitoring during construction of the sill would occur from an 
observation post adjacent to the Union Pacific railroad bridge as well 
as from a zodiac. Monitoring would be conducted by qualified, NMFS 
approved PSOs. On a daily basis, construction monitoring would begin 30 
minutes prior to the initiation of construction activities and continue 
until 30 minutes after construction activities have ceased for the day. 
The PSO would maintain a log that documents numbers of marine mammals 
present before, during, and at the end of daily construction 
activities. In addition, the PSO would record basic weather conditions 
(ambient temperature, tidal activity, precipitation, wind, horizontal 
visibility, etc.), as well as marine mammal behavior.
    The PSO would have the authority to cease construction if a harbor 
seal is detected within or approaching the safety zone or if an animal 
appears injured. Within 30 days of the completion of the sill 
construction, a report would be completed and submitted to NMFS that 
would include a summary of the daily log maintained by the PSO during 
construction. In addition, the report would include an assessment of 
the number of harbor seals that may have been harassed as a result of 
pile driving activities, based on direct observation of harbor seals 
observed in the area.

Estimated Take by Incidental Harassment

    Except with respect to certain activities not pertinent here, the 
MMPA defines ``harassment'' as: any act of pursuit, torment, or 
annoyance which (i) has the potential to injure a marine mammal or 
marine mammal stock in the wild [Level A harassment]; or (ii) has the 
potential to disturb a marine mammal stock in the wild by causing 
disruption of behavioral patterns, including but not limited to, 
migration, breathing, nursing, breeding, feeding, or shelter [Level B 
harassment].
    Based on the NOAA Restoration Center, Southwest Region's 
application and subsequent analysis, the impact of the described pile 
driving operations may result in, at most, short-term modification of 
behavior by small numbers of harbor seals within the action area. 
Harbor seals may avoid the area or halt any behaviors (e.g., resting) 
when exposed to anthropogenic noise. Due to the abundance of suitable 
resting habitat available in the greater Elkhorn Slough estuary, the 
short-term displacement of resting harbor seals is not expected to 
affect the overall fitness of any individual animal.
    Current NMFS practice regarding in-water exposure of marine mammals 
to anthropogenic noise is that in order to avoid the potential for 
injury of marine mammals (e.g., PTS), pinnipeds should not be exposed 
to impulsive sounds of 190 dB rms or above. This level is considered 
precautionary as it is likely that more intense sounds would be 
required before injury would actually occur (Southall et al., 2007). 
Potential for behavioral harassment (Level B) is considered to have 
occurred when marine mammals are exposed to sounds at or above 160 dB 
rms for impulse sounds (e.g., impact pile driving) and 120 dB rms for 
non-pulse noise (e.g., vibratory pile driving), but below the 
thresholds mentioned above. These levels are considered to be 
precautionary.
    Current NMFS practice regarding in-air exposure of pinnipeds to 
noise generated from human activity is that the onset of Level B 
harassment for harbor seals is 90 dB rms re 20 microPa. In-air noise 
calculations from using an impact pile driver predict that noise levels 
will reach 90 dB rms re 20 microPa within 600 ft (183 m) for end-
bearing piles and 450 ft (137 m) for sheet piles. For installation 
using a vibratory hammer, noise levels will reach 90 dB rms within 100 
ft (30 m) of the end-bearing pile and 120 ft (36.6 m) for sheet pile. 
Harbor seals are known to haul-out on the mudflats 200 ft (61 m) east 
of the work site and 680 ft (207 m) west of the work site, therefore, 
in-air noise may contribute to harassment for the proposed action.
    Estimated distances to NMFS' current threshold sound levels from 
pile driving during the Parsons Slough Sill Project are presented in 
Table 3. These estimates are based on the worst case scenario of 
driving the H-piles and sheet piles but would be carried over for all 
pile driving. Note that despite short distances to the Level A 
harassment isolpleth, the NOAA Restoration Center, Southwest Region, 
has proposed to implement a 10 m safety zone until empirical pile 
driving measurements can be made and distances to this threshold 
isopleths can be verified.

              Table 3--Underwater Distances to NMFS Harassment Threshold Levels During Pile Driving
                                              [dB re: 1[mu]Pa rms]
----------------------------------------------------------------------------------------------------------------
                                                                          Sound levels (rms)
            Pile type                 Hammer type    -----------------------------------------------------------
                                                            190 dB              160 dB              120 dB
----------------------------------------------------------------------------------------------------------------
H-Piles.........................  Impact............  3 m (10 ft).......  227 m (745 ft)....  n/a
H-Piles.........................  Vibratory.........  0.................  n/a...............  1,140 m (3,740 ft)
Sheet Pile......................  Impact............  1.5 m (5 ft)......  75 m (245 ft).....  n/a
Sheet Pile......................  Vibratory.........  0.................  n/a...............  2,256 m (7,400 ft)
----------------------------------------------------------------------------------------------------------------


[[Page 61439]]


 Table 4--Airborne Distances to NMFS Harassment Threshold Levels During
                              Pile Driving
                          [dB re: 20[mu]Pa rms]
------------------------------------------------------------------------
                                                      Sound level  (rms)
           Pile type                 Hammer type    --------------------
                                                            90 dB
------------------------------------------------------------------------
H-Piles........................  Impact............  600 m
H-Piles........................  Vibratory.........  100 m
Sheet Pile.....................  Impact............  450 m
Sheet Pile.....................  Vibratory.........  120 m
------------------------------------------------------------------------

    It is difficult to estimate the number of harbor seals that could 
be affected by the installation of end-bearing piles and sheet pile 
because the animals only venture in the project areas to haul-out 
during the day when the tide is low. In-water construction will occur 
near several haul-out sites and, although the construction activities 
are planned to take place during slack tide (some of which will be on 
either side of high tide, when harbor seals are less likely to be 
present), there may still be animals exposed to sound from pile driving 
even if the number of individual harbor seals expected to be 
encountered is very low. These individuals would mostly likely be adult 
males and females as well as juveniles. The NOAA Restoration Center, 
Southwest Region requests, and NMFS proposes, authorization to take 
2,000 individual harbor seals incidental to pile driving activities 
over the course of the proposed action (November 1, 2010 through 
February 28, 2011). This is a estimate based on the average number of 
harbor seals that occupy Parsons Slough during the day (100) multiplied 
by the total number of days the applicant expects pile driving 
activities to occur (20 days). NMFS considers this to be an over-
estimate for the following reasons: (1) As mentioned above, haul-out 
sites are inaccessible to harbor seals during high tide and NMFS would 
not expect harbor seals to be affected by pile driving activities 
during the days/times when pile driving and high tide events co-occur; 
(2) harbor seals are likely absent from Parsons Slough at night when 
they are likely foraging in Monterey Bay and will not be exposed to 
sound generated during pile driving that is proposed to take place in 
the evening hours (no more than 5 hrs at a time); and, (3) based on 
previous survey effort conducted in Parsons Slough, harbor seals would 
move out of the disturbance area when construction activities are 
initiated and move west (downstream) towards Seal Bend until the end of 
construction.

Negligible Impact and Small Numbers Analysis and Preliminary 
Determination

    The regulations implementing the MMPA found at 50 CFR 216.103 
define ``negligible impact'' 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. In making a negligible impact 
determination, NMFS considers a variety of factors, including but not 
limited to: (1) The number of anticipated mortalities (none of which 
would be authorized here); (2) the number and nature of anticipated 
injuries (none of which would be authorized here); and (3) the number, 
nature, and duration of Level B harassment, and the context in which 
the takes occur (e.g., will the takes occur in an area or time of 
significance for harbor seals, are takes occurring to a small, 
localized population?).
    As described above, harbor seals would not be exposed to activities 
or sound levels which would result in injury (e.g., PTS), serious 
injury, or mortality. Takes will be limited to Level B behavioral 
harassment. Pile driving would take place in the relatively shallow 
estuarine waters of Elkhorn Slough and affect harbor seals that belong 
to a stock that occurs throughout California. Although two harbor seal 
haul-outs are located within 300-400 ft of the action area (waters 
around the Union Pacific Railroad bridge), the Parsons Slough Complex 
is not considered to be an important habitat for harbor seals compared 
to other sites in the area (e.g. Seal Bend). NMFS has preliminarily 
determined that no injuries or mortalities are anticipated to occur as 
a result of the proposed action, and none are proposed to be 
authorized. In addition, harbor seals in the area are not expected to 
incur hearing impairment (i.e., TTS or PTS) or non-auditory 
physiological effects. Although it is possible for some individual 
harbor seals to be exposed to sounds from pile driving activities more 
than once, the extent of these multi-exposures are expected to be 
limited by the constant movement of harbor seals in and out of Elkhorn 
Slough and the timing of in-water construction to coincide with periods 
when the animals are less likely to be present.
    As previously mentioned Pacific harbor seals are not listed as 
depleted under the MMPA or threatened or endangered under the 
Endangered Species Act (ESA). Although populations of Pacific harbor 
seals were greatly depleted by the end of the 19th century due to 
commercial hunting, the population has increased dramatically during 
the last half of the 20th century and appears to be stabilizing at what 
may be their carrying capacity (Caretta et al., 2009). The amount of 
take the NOAA Restoration Center, Southwest Region, has requested, and 
NMFS proposes to authorize is considered small (less than 6 percent) 
relative to the estimated population of 34,233 Pacific harbor seals.
    Pacific harbor seals may be temporarily impacted by pile driving 
noise. However, these animals are expected to avoid the area, thereby 
reducing exposure and impacts. In addition, although the sill project 
is expected to take 11 to 15 weeks to complete, the installation of 
end-bearing piles and sheet pile would only occur for approximately 20 
days. Further, the Union Pacific Railroad bridge that is located in the 
vicinity of the project site has approximately 15-20 trains passing 
over it each day and harbor seals haul-out on the mud flats located on 
either side of the bridge. As mentioned earlier, during a previous 
project at this site involving pile driving, harbor seals were observed 
to be present during construction and reportedly entered and exited the 
area without any visible signs of stress or undue harassment (MACTEC 
Engineering and Consulting 2003). Therefore, animals are likely 
tolerant or habituated to anthropogenic disturbance, including pile 
driving. Finally, breeding and pupping occur outside of the proposed 
work window; therefore, no disruption to reproductive behavior is 
anticipated. There is no anticipated effect on annual rates of 
recruitment or survival of the affect harbor seal population.
    Based on the analysis contained herein of the likely effects of the 
specified activity on marine mammals and their habitat, and taking into 
consideration the implementation of the mitigation and monitoring 
measures, NMFS preliminarily determines that the Parsons Slough sill 
project will result in the incidental take of small numbers of marine 
mammals, by Level B harassment only, and that the total taking from the 
Parsons Slough project will have a negligible impact on the affected 
species or stocks.

Impact on Availability of Affected Species or Stock for Taking for 
Subsistence Uses

    There are no relevant subsistence uses of marine mammals implicated 
by this action.

[[Page 61440]]

Endangered Species Act (ESA)

    No ESA-listed species under NMFS' jurisdiction are expected to be 
affected by these activities. Therefore, NMFS has determined that a 
section 7 consultation for issuance of the proposed IHA under the ESA 
is not required.

National Environmental Policy Act (NEPA)

    Pursuant to NEPA, the general impacts associated with the design 
and construction phases of the proposed action are described in the 
Community-Based Restoration Program (CRP) Programmatic Environmental 
Assessment (PEA) and the Supplemental Programmatic Environmental 
Assessment (SPEA), which were prepared by the NOAA Restoration Center, 
Southwest Region. The NOAA Restoration Center, Southwest Region, will 
complete a Targeted Supplemental Environmental Assessment (TSEA) to 
include all project-specific impacts not described in the CRP PEA/SPEA. 
If it is adequate, NMFS will consider adopting it. If not, NMFS would 
prepare an independent EA. A copy of NOAA's EA can be obtained by going 
to the NMFS Web site listed in the beginning of this document. This 
analysis will be completed prior to the issuance or denial of this 
proposed IHA. The public is invited to provide comments on the 
potential effects to marine mammals disclosed in this notice as well as 
NOAA's EA. NMFS will consider public comments as it completes its NEPA 
analysis and decides whether or not to prepare a Finding of No 
Significant Impact should NMFS decide to issue a final IHA.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
authorize the take of marine mammals incidental to the Parsons Slough 
project, provided the previously mentioned mitigation, monitoring, and 
reporting requirements are incorporated.

    Dated: September 29, 2010.
Helen M. Golde,
Deputy Director, Office of Protected Resources, National Marine 
Fisheries Service.
[FR Doc. 2010-24986 Filed 10-4-10; 8:45 am]
BILLING CODE 3510-22-P