Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Bravo Wharf Recapitalization Project, 75978-75997 [2015-30745]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 80, Number 234 (Monday, December 7, 2015)]
[Notices]
[Pages 75978-75997]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-30745]


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

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

RIN 0648-XE271


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to the Bravo Wharf Recapitalization 
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 a request from the U.S. Navy (Navy) for 
authorization to take marine mammals incidental to construction 
activities as part of a wharf recapitalization project. Pursuant to the 
Marine Mammal Protection Act (MMPA), NMFS is requesting public comment 
on its proposal to issue an incidental harassment authorization (IHA) 
to the Navy to incidentally take marine mammals, by Level B harassment 
only, during the specified activity.

DATES: Comments and information must be received no later than January 
6, 2016.

ADDRESSES: Comments on this proposal should be addressed to Jolie 
Harrison, Chief, Permits and Conservation Division, Office of Protected 
Resources, National Marine Fisheries Service. Physical comments should 
be sent to 1315 East-West Highway, Silver Spring, MD 20910 and 
electronic comments should be sent to ITP.mccue@noaa.gov.
    Instructions: NMFS is not responsible for comments sent by any 
other method, to any other address or individual, or received after the 
end of the comment period. Comments received electronically, including 
all attachments, must not exceed a 25-megabyte file size. Attachments 
to electronic comments will be accepted in Microsoft Word or Excel or 
Adobe PDF file formats only. All comments received are a part of the 
public record and will generally be posted to the Internet at 
www.nmfs.noaa.gov/pr/permits/incidental/construction.htm without 
change. All personal identifying information (e.g., name, address) 
voluntarily submitted by the commenter may be publicly accessible. Do 
not submit confidential business information or otherwise sensitive or 
protected information.

FOR FURTHER INFORMATION CONTACT: Laura McCue, Office of Protected 
Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Availability

    An electronic copy of the Navy's application and supporting 
documents, as well as a list of the references cited in this document, 
may be obtained by visiting the Internet at: www.nmfs.noaa.gov/pr/permits/incidental/construction.htm. In case of problems accessing 
these documents, please call the contact listed above.

National Environmental Policy Act

    The Navy has prepared a draft Environmental Assessment (Wharf Bravo 
Recapitalization at Naval Station Mayport, Jacksonville, FL) in 
accordance with the National Environmental Policy Act (NEPA) and the 
regulations published by the Council on Environmental Quality. It is 
posted at the aforementioned site. NMFS will independently evaluate the 
EA and determine whether or not to adopt it. We may prepare a separate 
NEPA analysis and incorporate relevant portions of Navy's EA by 
reference. Information in the Navy's application, EA, and this notice 
collectively provide the environmental information related to proposed 
issuance of this IHA for public review and comment. We will review all 
comments submitted in response to this notice as we complete the NEPA 
process, including a decision of whether to sign a Finding of No 
Significant Impact (FONSI), prior to a final decision on the incidental 
take authorization request.

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 by U.S. 
citizens who engage in a specified activity (other than commercial 
fishing) within a specified area, the incidental, but not intentional, 
taking of small numbers of marine mammals, providing that certain 
findings are made and the necessary prescriptions are established.
    The incidental taking of small numbers of marine mammals may be 
allowed only if NMFS (through authority delegated by the Secretary) 
finds that the total taking by the specified activity during the 
specified time period will (i) have a negligible impact on the species 
or stock(s) and (ii) not have an unmitigable adverse impact on the 
availability of the species or stock(s) for subsistence uses (where 
relevant). Further, the permissible methods of taking and requirements 
pertaining to the mitigation, monitoring and reporting of such taking 
must be set forth, either in specific regulations or in an 
authorization.
    The allowance of such incidental taking under section 101(a)(5)(A), 
by harassment, serious injury, death, or a combination thereof, 
requires that regulations be established. Subsequently, a Letter of 
Authorization may be issued pursuant to the prescriptions established 
in such regulations, providing that the level of taking will be 
consistent with the findings made for the total taking allowable under 
the specific regulations. Under section 101(a)(5)(D), NMFS may 
authorize such incidental taking by harassment only, for periods of not 
more than one year, pursuant to requirements and conditions contained 
within an IHA. The establishment of prescriptions through either 
specific regulations or an authorization requires notice and 
opportunity for public comment.
    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.'' Except with respect to certain activities 
not pertinent here, section 3(18) of 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

    On July 21, 2015, we received a request from the Navy for 
authorization of the taking, by Level B harassment only, of marine 
mammals, incidental to pile driving in association with the

[[Page 75979]]

Bravo Wharf recapitalization project at Naval Station Mayport, Florida 
(NSM). That request was modified on November 4 and November 10, and a 
final version, which we deemed adequate and complete, was submitted on 
November 17. In-water work associated with the project is expected to 
be completed within the one-year timeframe of the proposed IHA (October 
15, 2016 through September 30, 2017).
    The use of both vibratory and impact pile driving is expected to 
produce underwater sound at levels that have the potential to result in 
behavioral harassment of marine mammals. One species of marine mammal 
has the potential to be affected by the specified activities: 
bottlenose dolphin (Tursiops truncatus truncatus). This species may 
occur year-round in the action area.
    Similar wharf construction and pile driving activities in Naval 
Station Mayport have been authorized by NMFS in the past. The first 
authorization was effective between September 1, 2014 through August 
31, 2015, and the second authorization, which is currently ongoing, is 
effective from September 8, 2015 through September 7, 2016.

Description of the Specified Activity

Overview

    Bravo Wharf is a medium draft, general purpose berthing wharf that 
was constructed in 1970 and lies at the western edge of the NSM turning 
basin. Bravo Wharf is approximately 2,000 ft long, 125 ft wide, and has 
a berthing depth of 50 ft mean lower low water. The wharf is one of two 
primary deep draft berths at the basin and is capable of berthing ships 
up to and including large amphibious ships; it is one of three primary 
ordnance handling berths at the basin. The wharf is a diaphragm steel 
sheet pile cell structure with a concrete apron, partial concrete 
encasement of the piling and asphalt paved deck. The wharf is currently 
in poor condition due to advanced deterioration of the steel sheeting 
and lack of corrosion protection. This structural deterioration has 
resulted in the institution of load restrictions within 60 ft of the 
wharf face. The purpose of this project is to complete necessary 
repairs to Bravo Wharf. Please refer to the Navy's application for a 
schematic of the project plan.

Dates and Duration

    The total project is expected to require a maximum of 130 days of 
in-water pile driving. The project may require up to 24 months for 
completion; in-water activities are limited to a maximum of 130 days, 
separated into two phases. If in-water work will extend beyond the 
effective dates of the IHA, a second IHA application will be submitted 
by the Navy. There will be a maximum of 110 days for vibratory pile 
driving (seventy three days in phase I and thirty seven days in phase 
II), and a contingent 20 days of impact pile driving. The specified 
activities are expected to occur between October 1, 2016 and September 
30, 2017.

Specific Geographic Region

    NSM is located in northeastern Florida, at the mouth of the St. 
Johns River and adjacent to the Atlantic Ocean (see Figures 2-1 and 2-2 
of the Navy's application). The St. Johns River is the longest river in 
Florida, with the final 35 mi flowing through the city of Jacksonville. 
This portion of the river is significant for commercial shipping and 
military use. At the mouth of the river, near the action area, the 
Atlantic Ocean is the dominant influence and typical salinities are 
above 30 ppm. Outside the river mouth, in nearshore waters, moderate 
oceanic currents tend to flow southward parallel to the coast. Sea 
surface temperatures range from around 16 [deg]C in winter to 28 [deg]C 
in summer.
    The specific action area consists of the NSM turning basin, an area 
of approximately 2,000 by 3,000 ft containing ship berthing facilities 
at sixteen locations along wharves around the basin perimeter. The 
basin was constructed during the early 1940s by dredging the eastern 
part of Ribault Bay (at the mouth of the St. Johns River), with dredge 
material from the basin used to fill parts of the bay and other low-
lying areas in order to elevate the land surface. The basin is 
currently maintained through regular dredging at a depth of 50 ft, with 
depths at the berths ranging from 30-50 ft. The turning basin, 
connected to the St. Johns River by a 500-ft-wide entrance channel, 
will largely contain sound produced by project activities, with the 
exception of sound propagating east into nearshore Atlantic waters 
through the entrance channel (see Figure 2-2 of the Navy's 
application). Bravo Wharf is located in the western corner of the 
Mayport turning basin.

Detailed Description of Activities

    In order to rehabilitate Bravo Wharf, the Navy proposes to install 
a new steel sheet pile bulkhead at Bravo Wharf. The project consists of 
installing a total of approximately 880 single sheet piles (Phase I--
berths B-2 and B-3: 590; Phase II--berth B-1: 290). The wall will be 
anchored at the top and fill consisting of clean gravel and flowable 
concrete fill will be placed behind the wall. A concrete cap will be 
formed along the top and outside face of the wall to tie the entire 
structure together and provide a berthing surface for vessels. The new 
bulkhead will be designed for a fifty-year service life.
    All piles would be driven by vibratory hammer, although impact pile 
driving may be used as a contingency in cases when vibratory driving is 
not sufficient to reach the necessary depth. In the unlikely event that 
impact driving is required, either impact or vibratory driving could 
occur on a given day, but concurrent use of vibratory and impact 
drivers would not occur. The Navy estimates that a total of 130 in-
water work days may be required to complete pile driving activity, 
which includes twenty days for contingency impact driving, if 
necessary.

Description of Marine Mammals in the Area of the Specified Activity

    There are four marine mammal species which may inhabit or transit 
through the waters nearby NSM at the mouth of the St. Johns River and 
in nearby nearshore Atlantic waters. These include the bottlenose 
dolphin, Atlantic spotted dolphin (Stenella frontalis), North Atlantic 
right whale (Eubalaena glacialis), and humpback whale (Megaptera 
novaeangliae). Multiple additional cetacean species occur in South 
Atlantic waters but would not be expected to occur in shallow nearshore 
waters of the action area. Table 1 lists the marine mammal species with 
expected potential for occurrence in the vicinity of NSM during the 
project timeframe and summarizes key information regarding stock status 
and abundance. Taxonomically, we follow Committee on Taxonomy (2014). 
Please see NMFS' Stock Assessment Reports (SAR), available at 
www.nmfs.noaa.gov/pr/sars, for more detailed accounts of these stocks' 
status and abundance. Please also refer to NMFS' Web site 
(www.nmfs.noaa.gov/pr/species/mammals) for generalized species accounts 
and to the Navy's Marine Resource Assessment for the Charleston/
Jacksonville Operating Area, which documents and describes the marine 
resources that occur in Navy operating areas of the Southeast (DoN, 
2008). The document is publicly available at www.navfac.navy.mil/products_and_services/ev/products_and_services/marine_resources/marine_resource_assessments.html (accessed November 2, 2015).
    In the species accounts provided here, we offer a brief 
introduction to the species and relevant stock as well as available 
information regarding population trends and threats, and

[[Page 75980]]

describe any information regarding local occurrence. Multiple stocks of 
bottlenose dolphins may be present in the action area, either 
seasonally or year-round, and are described further below. We first 
address the three other species that may occur in the action area.

                                           Table 1--Marine Mammals Potentially Present in the Vicinity of NSM
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                     Stock abundance  (CV,
              Species                         Stock             ESA/MMPA status;       Nmin, most recent     PBR \3\   Annual M/   Relative occurrence;
                                                              strategic  (Y/N) \1\   abundance survey) \2\               SI \4\    season of occurrence
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                          Order Cetartiodactyla--Cetacea--Superfamily Mysticeti (baleen whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    Family Balaenidae
--------------------------------------------------------------------------------------------------------------------------------------------------------
North Atlantic right whale.........  Western North Atlantic  E/D; Y                 476 (0; 476; 2013)....          1        4.3  Rare inshore, regular
                                      \5\.                                                                                         near/offshore; Nov-
                                                                                                                                   Apr.
Humpback whale.....................  Gulf of Maine.........  E/D; Y                 823 (0; 823; 2008)....        2.7        7.6  Rare; Fall-Spring.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                            Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   Family Delphinidae
--------------------------------------------------------------------------------------------------------------------------------------------------------
Atlantic spotted dolphin...........  Western North Atlantic  -; N                   44,715 (0.43; 31,610;         316          0  Rare; year-round.
                                                                                     2011).
Common bottlenose dolphin..........  Western North Atlantic  -; N                   77,532 (0.4; 56,053;          561       43.9  Rare; year-round.
                                      Offshore.                                      2011).
                                     Western North Atlantic  -/D; Y                 9,173 (0.46; 6,326;            63       0-12  Possibly common; \8\
                                      Coastal, Southern                              2010-11).                                     Jan-Mar.
                                      Migratory.
                                     Western North Atlantic  -/D; Y                 1,219 (0.67; 730; 2010-         7        0.4  Possibly common; \8\
                                      Coastal, Northern                              11).                                          year-round.
                                      Florida.
                                     Jacksonville Estuarine  -; Y                   412 \7\ (0.06; unk;        undet.        1.2  Possibly common; \8\
                                      System \6\.                                    1994-97).                                     year-round.
--------------------------------------------------------------------------------------------------------------------------------------------------------
 
\1\ ESA status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or
  designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR (see
  footnote 3) or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed
  under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
\2\ CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable. For certain stocks, abundance
  estimates are actual counts of animals and there is no associated CV. The most recent abundance survey that is reflected in the abundance estimate is
  presented; there may be more recent surveys that have not yet been incorporated into the estimate.
\3\ Potential biological removal, defined by the MMPA as the maximum number of animals, not including natural mortalities, that may be removed from a
  marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population size (OSP).
\4\ These values, found in NMFS' SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g., commercial
  fisheries, subsistence hunting, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value. All
  values presented here are from the draft 2015 SARs (www.nmfs.noaa.gov/pr/sars/draft.htm).
\5\ Abundance estimates (and resulting PBR values) for these stocks are new values presented in the draft 2015 SARs. This information was made available
  for public comment and is currently under review and therefore may be revised prior to finalizing the 2015 SARs. However, we consider this information
  to be the best available for use in this document.
\6\ Abundance estimates for these stocks are greater than eight years old and are therefore not considered current. PBR is considered undetermined for
  these stocks, as there is no current minimum abundance estimate for use in calculation. We nevertheless present the most recent abundance estimates
  and PBR values, as these represent the best available information for use in this document.
\7\ This abundance estimate is considered an overestimate because it includes non- and seasonally-resident animals.
\8\ Bottlenose dolphins in general are common in the project area, but it is not possible to readily identify them to stock. Therefore, these three
  stocks are listed as possibly common as we have no information about which stock commonly only occurs.

    Northern Right whales occur in sub-polar to temperate waters in all 
major ocean basins in the world with a clear migratory pattern, 
occurring in high latitudes in summer (feeding) and lower latitudes in 
winter (breeding). North Atlantic right whales exhibit extensive 
migratory patterns, traveling along the eastern seaboard from calving 
grounds off Georgia and northern Florida to northern feeding areas off 
of the northeast U.S. and Canada in March/April and returning in 
November/December. Migrations are typically within 30 nmi of the 
coastline and in waters less than 50 m deep. Although this migratory 
pattern is well known, winter distribution for most of the population--
the non-calving portion--is poorly known, as many whales are not 
observed on the calving grounds. It is unknown where these animals 
spend the winter, although they may occur further offshore or may 
remain on foraging grounds during winter (Morano et al., 2012). During 
the winter calving period, right whales occur regularly in offshore 
waters of northeastern Florida. Critical habitat for right whales in 
the southeast (as identified under the ESA) is designated to protect 
calving grounds, and encompasses waters from the coast out to 15 nmi 
offshore from Mayport. More rarely, right whales have been observed 
entering the mouth of the St. Johns River for brief periods of time 
(Schweitzer and Zoodsma, 2011). Right whales are not present in the 
region outside of the winter calving season.
    Humpback whales are a cosmopolitan species that migrate seasonally 
between warm-water (tropical or sub-tropical) breeding and calving 
areas in winter months and cool-water (temperate to sub-Arctic/
Antarctic) feeding areas in summer months (Gendron and Urban, 1993). 
They tend to occupy shallow, coastal waters, although migrations are

[[Page 75981]]

undertaken through deep, pelagic waters. In the North Atlantic, 
humpback whales are known to aggregate in six summer feeding areas 
representing relatively discrete subpopulations (Clapham and Mayo, 
1987), which share common wintering grounds in the Caribbean (and to a 
lesser extent off of West Africa) (Winn et al., 1975; Mattila et al., 
1994; Palsb[oslash]ll et al., 1997; Smith et al., 1999; Stevick et al., 
2003; Cerchio et al., 2010). These populations or aggregations range 
from the Gulf of Maine in the west to Norway in the east, and the 
migratory range includes the east coast of the U.S. and Canada. The 
only managed stock in U.S. waters is the Gulf of Maine feeding 
aggregation, although other stocks occur in Canadian waters (e.g., Gulf 
of St. Lawrence feeding aggregation), and it is possible that whales 
from other stocks could occur in U.S. waters. Significant numbers of 
whales do remain in mid- to high-latitude waters during the winter 
months (Clapham et al., 1993; Swingle et al., 1993), and there have 
been a number of humpback sightings in coastal waters of the 
southeastern U.S. during the winter (Wiley et al., 1995; Laerm et al., 
1997; Waring et al., 2014). According to Waring et al. (2014), it is 
unclear whether the increased numbers of sightings represent a 
distributional change, or are simply due to an increase in sighting 
effort and/or whale abundance. These factors aside, the humpback whale 
remains relatively rare in U.S. coastal waters south of the mid-
Atlantic region, and is considered rare to extralimital in the action 
area. Any occurrences in the region would be expected in fall, winter, 
and spring during migration, as whales are unlikely to occur so far 
south during the summer feeding season.
    Neither the humpback whale nor the right whale would occur within 
the turning basin, and only the right whale has been observed to occur 
as far inshore as the mouth of the St. Johns River. Therefore, the 
potential for interaction with these species is unlikely. When 
considering frequency of occurrence, size of ensonified area (less than 
one square kilometer during both vibratory (approximately 0.61 km\2\) 
and impact driving (0.51 km\2\)), and duration (seventy three days in 
phase I, and thirty seven days in phase II), we consider the 
possibility for harassment of humpback and right whales to be 
discountable. Therefore, the humpback whale and right whale are 
excluded from further analysis and are not discussed further in this 
document.
    Atlantic spotted dolphins are distributed in tropical and warm 
temperate waters of the western North Atlantic predominantly over the 
continental shelf and upper slope, from southern New England through 
the Gulf of Mexico (Leatherwood et al., 1976). Spotted dolphins in the 
Atlantic Ocean and Gulf of Mexico are managed as separate stocks. The 
Atlantic spotted dolphin occurs in two forms which may be distinct sub-
species (Perrin et al., 1987; Rice, 1998); a larger, more heavily 
spotted form inhabits the continental shelf inside or near the 200-m 
isobath and is the only form that would be expected to occur in the 
action area. Although typically observed in deeper waters, spotted 
dolphins of the western North Atlantic stock do occur regularly in 
nearshore waters south of the Chesapeake Bay (Mullin and Fulling, 
2003). Specific data regarding seasonal occurrence in the region of 
activity is lacking, but higher numbers of individuals have been 
reported to occur in nearshore waters of the Gulf of Mexico from 
November to May, suggesting seasonal migration patterns (Griffin and 
Griffin, 2003).
    From recent observation reports from the Navy from previous 
construction activity at Naval Station Mayport, no spotted dolphins 
were observed. Similarly, dolphin research studies that have been 
conducted in the area also reported zero observed spotted dolphins in 
the project area (Gibson, pers. comm.). We consider the likelihood of 
Atlantic spotted dolphins being impacted by the construction activities 
to be discountable based on this information, combined with the zero 
estimated exposures (density: 0.005240/km\2\). Therefore, spotted 
dolphins are also excluded from further analysis and are not discussed 
further in this document.
    The following summarizes the population status and abundance of the 
remaining species.

Bottlenose Dolphin

    Bottlenose dolphins are found worldwide in tropical to temperate 
waters and can be found in all depths from estuarine inshore to deep 
offshore waters. Temperature appears to limit the range of the species, 
either directly, or indirectly, for example, through distribution of 
prey. Off North American coasts, common bottlenose dolphins are found 
where surface water temperatures range from about 10 [deg]C to 32 
[deg]C. In many regions, including the southeastern U.S., separate 
coastal and offshore populations are known. There is significant 
genetic, morphological, and hematological differentiation evident 
between the two ecotypes (e.g., Walker, 1981; Duffield et al., 1983; 
Duffield, 1987; Hoelzel et al., 1998), which correspond to shallow, 
warm water and deep, cold water. Both ecotypes have been shown to 
inhabit the western North Atlantic (Hersh and Duffield, 1990; Mead and 
Potter, 1995), where the deep-water ecotype tends to be larger and 
darker. In addition, several lines of evidence, including photo-
identification and genetic studies, support a distinction between 
dolphins inhabiting coastal waters near the shore and those present in 
the inshore waters of bays, sounds and estuaries. This complex 
differentiation of bottlenose dolphin populations is observed 
throughout the Atlantic and Gulf of Mexico coasts where bottlenose 
dolphins are found, although estuarine populations have not been fully 
defined.
    In the Mayport area, four stocks of bottlenose dolphins are 
currently managed, none of which are protected under the ESA. Of the 
four stocks--offshore, southern migratory coastal, northern Florida 
coastal, and Jacksonville estuarine system--only the latter three are 
likely to occur in the action area. Bottlenose dolphins typically occur 
in groups of 2-15 individuals (Shane et al., 1986; Kerr et al., 2005). 
Although significantly larger groups have also been reported, smaller 
groups are typical of shallow, confined waters. In addition, such 
waters typically support some degree of regional site fidelity and 
limited movement patterns (Shane et al., 1986; Wells et al., 1987). 
Observations made during marine mammal surveys conducted during 2012-
2013 in the Mayport turning basin show bottlenose dolphins typically 
occurring individually or in pairs, or less frequently in larger 
groups. The maximum observed group size during these surveys is six, 
while the mode is one. Navy observations indicate that bottlenose 
dolphins rarely linger in a particular area in the turning basin, but 
rather appear to move purposefully through the basin and then leave, 
which likely reflects a lack of biological importance for these 
dolphins in the basin. Based on currently available information, it is 
not possible to determine the stock to which the dolphins occurring in 
the action area may belong. These stocks are described in greater 
detail below.
    Western North Atlantic Offshore--This stock, consisting of the 
deep-water ecotype or offshore form of bottlenose dolphin in the 
western North Atlantic, is distributed primarily along the outer 
continental shelf and continental slope, but has been documented to 
occur relatively close to shore (Waring et al., 2014). The separation 
between offshore and coastal morphotypes varies

[[Page 75982]]

depending on location and season, with the ranges overlapping to some 
degree south of Cape Hatteras. Based on genetic analysis, Torres et al. 
(2003) found a distributional break at 34 km from shore, with the 
offshore form found exclusively seaward of 34 km and in waters deeper 
than 34 m. Within 7.5 km of shore, all animals were of the coastal 
morphotype. More recently, coastwide, systematic biopsy collection 
surveys were conducted during the summer and winter to evaluate the 
degree of spatial overlap between the two morphotypes. South of Cape 
Hatteras, spatial overlap was found although the probability of a 
sampled group being from the offshore morphotype increased with 
increasing depth, and the closest distance for offshore animals was 7.3 
km from shore, in water depths of 13 m just south of Cape Lookout 
(Garrison et al., 2003). The maximum radial distance for the largest 
ZOI is approximately 1.2 km (Table 3); therefore, it is unlikely that 
any individuals of the offshore morphotype would be affected by project 
activities. In terms of water depth, the affected area is generally in 
the range of the shallower depth reported for offshore dolphins by 
Garrison et al. (2003), but is far shallower than the depths reported 
by Torres et al. (2003). South of Cape Lookout, the zone of spatial 
overlap between offshore and coastal ecotypes is generally considered 
to occur in water depths between 20-100 m (Waring et al., 2014), which 
is generally deeper than waters in the action area. This stock is thus 
excluded from further analysis.
    Western North Atlantic Coastal, Southern Migratory--The coastal 
morphotype of bottlenose dolphin is continuously distributed from the 
Gulf of Mexico to the Atlantic and north approximately to Long Island 
(Waring et al., 2014). On the Atlantic coast, Scott et al. (1988) 
hypothesized a single coastal stock, citing stranding patterns during a 
high mortality event in 1987-88 and observed density patterns. More 
recent studies demonstrate that there is instead a complex mosaic of 
stocks (Zolman, 2002; McLellan et al., 2002; Rosel et al., 2009). The 
coastal morphotype was managed by NMFS as a single stock until 2009, 
when it was split into five separate stocks, including northern and 
southern migratory stocks. The original, single stock of coastal 
dolphins recognized from 1995-2001 was listed as depleted under the 
MMPA as a result of a 1987-88 mortality event. That designation was 
retained when the single stock was split into multiple coastal stocks. 
Therefore, all coastal stocks of bottlenose dolphins are listed as 
depleted under the MMPA, and are also considered strategic stocks.
    According to the Scott et al. (1988) hypothesis, a single stock was 
thought to migrate seasonally between New Jersey (summer) and central 
Florida (winter). Instead, it was more recently determined that a mix 
of resident and migratory stocks exists, with the migratory movements 
and spatial distribution of the southern migratory stock the most 
poorly understood of these. Stable isotope analysis and telemetry 
studies provide evidence for seasonal movements of dolphins between 
North Carolina and northern Florida (Knoff, 2004; Waring et al., 2014), 
and genetic analyses and tagging studies support differentiation of 
northern and southern migratory stocks (Rosel et al., 2009; Waring et 
al., 2014). Although there is significant uncertainty regarding the 
southern migratory stock's spatial movements, telemetry data indicates 
that the stock occupies waters of southern North Carolina (south of 
Cape Lookout) during the fall (October-December). In winter months 
(January-March), the stock moves as far south as northern Florida where 
it overlaps spatially with the northern Florida coastal and 
Jacksonville estuarine system stocks. In spring (April-June), the stock 
returns north to waters of North Carolina, and is presumed to remain 
north of Cape Lookout during the summer months. Therefore, the 
potential exists for harassment of southern migratory dolphins, most 
likely during the winter only.
    Bottlenose dolphins are ubiquitous in coastal waters from the mid-
Atlantic through the Gulf of Mexico, and therefore interact with 
multiple coastal fisheries, including gillnet, trawl, and trap/pot 
fisheries. Stock-specific total fishery-related mortality and serious 
injury cannot be directly estimated because of the spatial overlap 
among stocks of bottlenose dolphins, as well as because of unobserved 
fisheries. The primary known source of fishery mortality for the 
southern migratory stock is the mid-Atlantic gillnet fishery (Waring et 
al., 2014). Between 2004 and 2008, 588 bottlenose dolphins stranded 
along the Atlantic coast between Florida and Maryland that could 
potentially be assigned to the southern migratory stock, although the 
assignment of animals to a particular stock is impossible in some 
seasons and regions due to spatial overlap amongst stocks (Waring et 
al., 2014). Many of these animals exhibited some evidence of human 
interaction, such as line/net marks, gunshot wounds, or vessel strike. 
In addition, nearshore and estuarine habitats occupied by the coastal 
morphotype are adjacent to areas of high human population and some are 
highly industrialized. It should also be noted that stranding data 
underestimate the extent of fishery-related mortality and serious 
injury because not all of the marine mammals that die or are seriously 
injured in fishery interactions are discovered, reported or 
investigated, nor will all of those that are found necessarily show 
signs of entanglement or other fishery interaction. The level of 
technical expertise among stranding network personnel varies widely as 
does the ability to recognize signs of fishery interactions. Finally, 
multiple resident populations of bottlenose dolphins have been shown to 
have high concentrations of organic pollutants (e.g., Kuehl et al., 
1991) and, despite little study of contaminant loads in migrating 
coastal dolphins, exposure to environmental pollutants and subsequent 
effects on population health is an area of concern and active research.
    Western North Atlantic Coastal, Northern Florida--Please see above 
for description of the differences between coastal and offshore 
ecotypes and the delineation of coastal dolphins into management 
stocks. The northern Florida coastal stock is one of five stocks of 
coastal dolphins and one of three known resident stocks (other resident 
stocks include South Carolina/Georgia and central Florida dolphins). 
The spatial extent of these stocks, their potential seasonal movements, 
and their relationships with estuarine stocks are poorly understood. 
During summer months, when the migratory stocks are known to be in 
North Carolina waters and further north, bottlenose dolphins are still 
seen in coastal waters of South Carolina, Georgia and Florida, 
indicating the presence of additional stocks of coastal animals. 
Speakman et al. (2006) documented dolphins in coastal waters off 
Charleston, South Carolina, that are not known resident members of the 
estuarine stock, and genetic analyses indicate significant differences 
between coastal dolphins from northern Florida, Georgia and central 
South Carolina (NMFS, 2001; Rosel et al., 2009). The northern Florida 
stock is thought to be present from approximately the Georgia-Florida 
border south to 29.4[deg] N. (Waring et al., 2014).
    The northern Florida coastal stock ventures into the St. Johns 
River in large numbers, but rarely moves past Naval Station Mayport. 
The mouth of the St. Johns River may serve as a foraging area for this 
stock and the Jacksonville estuarine stock (Gibson, pers. comm).

[[Page 75983]]

    The northern Florida coastal stock is susceptible to interactions 
with similar fisheries as those described above for the southern 
migratory stock, including gillnet, trawl, and trap/pot fisheries. From 
2004-08, 78 stranded dolphins were recovered in northern Florida 
waters, although it was not possible to determine whether there was 
evidence of human interaction for the majority of these (Waring et al., 
2014). The same concerns discussed above regarding underestimation of 
mortality hold for this stock and, as for southern migratory dolphins, 
pollutant loading is a concern.
    Jacksonville Estuarine System--Please see above for description of 
the differences between coastal and offshore ecotypes and the 
delineation of coastal dolphins into management stocks primarily 
inhabiting nearshore waters. The coastal morphotype of bottlenose 
dolphin is also resident to certain inshore estuarine waters (Caldwell, 
2001; Gubbins, 2002; Zolman, 2002; Gubbins et al., 2003). Multiple 
lines of evidence support demographic separation between coastal 
dolphins found in nearshore waters and those in estuarine waters, as 
well as between dolphins residing within estuaries along the Atlantic 
and Gulf coasts (e.g., Wells et al., 1987; Scott et al., 1990; Wells et 
al., 1996; Cortese, 2000; Zolman, 2002; Speakman, et al. 2006; Stolen 
et al., 2007; Balmer et al., 2008; Mazzoil et al., 2008). In 
particular, a study conducted near Jacksonville demonstrated 
significant genetic differences between coastal and estuarine dolphins 
(Caldwell, 2001; Rosel et al., 2009). Despite evidence for genetic 
differentiation between estuarine and nearshore populations, the degree 
of spatial overlap between these populations remains unclear. Photo-
identification studies within estuaries demonstrate seasonal 
immigration and emigration and the presence of transient animals (e.g., 
Speakman et al., 2006). In addition, the degree of movement of resident 
estuarine animals into coastal waters on seasonal or shorter time 
scales is poorly understood (Waring et al., 2014).
    The Jacksonville estuarine system (JES) stock has been defined as 
separate primarily by the results of photo-identification and genetic 
studies. The stock range is considered to be bounded in the north by 
the Georgia-Florida border at Cumberland Sound, extending south to 
approximately Jacksonville Beach, Florida. This encompasses an area 
defined during a photo-identification study of bottlenose dolphin 
residency patterns in the area (Caldwell, 2001), and the borders are 
subject to change upon further study of dolphin residency patterns in 
estuarine waters of southern Georgia and northern/central Florida. The 
habitat is comprised of several large brackish rivers, including the 
St. Johns River, as well as tidal marshes and shallow riverine systems. 
Three behaviorally different communities were identified during 
Caldwell's (2001) study: The estuarine waters north (Northern) and 
south (Southern) of the St. Johns River and the coastal area, all of 
which differed in density, habitat fidelity and social affiliation 
patterns. The coastal dolphins are believed to be members of a coastal 
stock, however (Waring et al., 2014). Although Northern and Southern 
members of the JES stock show strong site fidelity, members of both 
groups have been observed outside their preferred areas. Dolphins 
residing within estuaries south of Jacksonville Beach down to the 
northern boundary of the Indian River Lagoon Estuarine System (IRLES) 
stock are currently not included in any stock, as there are 
insufficient data to determine whether animals in this area exhibit 
affiliation to the JES stock, the IRLES stock, or are simply transient 
animals associated with coastal stocks. Further research is needed to 
establish affinities of dolphins in the area between the ranges, as 
currently understood, of the JES and IRLES stocks.
    The JES stock is susceptible to similar fisheries interactions as 
those described above for coastal stocks, although only trap/pot 
fisheries are likely to occur in estuarine waters frequented by the 
stock. Only one dolphin carcass bearing evidence of fisheries 
interaction was recovered during 2003-07 in the JES area, and an 
additional sixteen stranded dolphins were recovered during this time, 
but no determinations regarding human interactions could be made for 
the majority (Waring et al., 2014). Nineteen bottlenose dolphins died 
in the St. Johns River (SJR), Florida between May 24 and November 7, 
2010, all of which came from the JES stock. The cause of these deaths 
was undetermined. The same concerns discussed above regarding 
underestimation of mortality hold for this stock and, as for stocks 
discussed above, pollutant loading is a concern. Although no 
contaminant analyses have yet been conducted in this area, the JES 
stock inhabits areas with significant drainage from industrial and 
urban sources, and as such is exposed to contaminants in runoff from 
these. In other estuarine areas where such analyses have been 
conducted, exposure to anthropogenic contaminants has been found to 
likely have an effect (Hansen et al. 2004; Schwacke et al., 2004; Reif 
et al., 2008).
    The original, single stock of coastal dolphins recognized from 
1995-2001 was listed as depleted under the MMPA as a result of a 1987-
88 mortality event. That designation was retained when the single stock 
was split into multiple coastal stocks. However, Scott et al. (1988) 
suggested that dolphins residing in the bays, sounds and estuaries 
adjacent to these coastal waters were not affected by the mortality 
event and these animals were explicitly excluded from the depleted 
listing (Waring et al., 2014). Gubbins et al. (2003), using data from 
Caldwell (2001), estimated the stock size to be 412 (CV = 0.06). 
However, NMFS considers abundance unknown because this estimate likely 
includes an unknown number of non-resident and seasonally-resident 
dolphins. It nevertheless represents the best available information 
regarding stock size. Because the stock size is likely small, and 
relatively few mortalities and serious injuries would exceed PBR, the 
stock is considered to be a strategic stock (Waring et al., 2014).
    An unusual mortality event (UME) occurred between 2013 and 2015 
spanning the Atlantic coast, which impacted all stocks of bottlenose 
dolphins in the area. Over 1,800 dolphins stranded in this time period. 
The preliminary conclusion of the cause of this UME was morbillivirus. 
The bottlenose dolphin stocks in this area (SJR and coastal areas) may 
be considered vulnerable to impacts from future activities due to this 
recent event.

Potential Effects of the Specified Activity on Marine Mammals and Their 
Habitat

    This section includes a summary and discussion of the ways that 
components of the specified activity (e.g., sound produced by pile 
driving) may impact marine mammals and their habitat. The Estimated 
Take by Incidental Harassment section later in this document will 
include a quantitative analysis of the number of individuals that are 
expected to be taken by this activity. The Negligible Impact Analysis 
section will include an analysis of how this specific activity will 
impact marine mammals and will consider the content of this section, 
the Estimated Take by Incidental Harassment section and the Proposed 
Mitigation section to draw conclusions regarding the likely impacts of 
this activity on the reproductive success or survivorship of 
individuals and from that on the affected marine mammal populations or 
stocks. In the following discussion, we provide general background 
information on

[[Page 75984]]

sound and marine mammal hearing before considering potential effects to 
marine mammals from sound produced by vibratory and impact pile 
driving.

Description of Sound Sources

    Sound travels in waves, the basic components of which are 
frequency, wavelength, velocity, and amplitude. Frequency is the number 
of pressure waves that pass by a reference point per unit of time and 
is measured in hertz (Hz) or cycles per second. Wavelength is the 
distance between two peaks of a sound wave; lower frequency sounds have 
longer wavelengths than higher frequency sounds and attenuate 
(decrease) more rapidly in shallower water. Amplitude is the height of 
the sound pressure wave or the `loudness' of a sound and is typically 
measured using the decibel (dB) scale. A dB is the ratio between a 
measured pressure (with sound) and a reference pressure (sound at a 
constant pressure, established by scientific standards). It is a 
logarithmic unit that accounts for large variations in amplitude; 
therefore, relatively small changes in dB ratings correspond to large 
changes in sound pressure. When referring to sound pressure levels 
(SPLs; the sound force per unit area), sound is referenced in the 
context of underwater sound pressure to 1 microPascal ([mu]Pa). One 
pascal is the pressure resulting from a force of one newton exerted 
over an area of one square meter. The source level (SL) represents the 
sound level at a distance of 1 m from the source (referenced to 1 
[mu]Pa). The received level is the sound level at the listener's 
position. Note that all underwater sound levels in this document are 
referenced to a pressure of 1 [micro]Pa and all airborne sound levels 
in this document are referenced to a pressure of 20 [mu]Pa.
    Root mean square (rms) is the quadratic mean sound pressure over 
the duration of an impulse. Rms is calculated by squaring all of the 
sound amplitudes, averaging the squares, and then taking the square 
root of the average (Urick, 1983). Rms accounts for both positive and 
negative values; squaring the pressures makes all values positive so 
that they may be accounted for in the summation of pressure levels 
(Hastings and Popper, 2005). This measurement is often used in the 
context of discussing behavioral effects, in part because behavioral 
effects, which often result from auditory cues, may be better expressed 
through averaged units than by peak pressures.
    When underwater objects vibrate or activity occurs, sound-pressure 
waves are created. These waves alternately compress and decompress the 
water as the sound wave travels. Underwater sound waves radiate in all 
directions away from the source (similar to ripples on the surface of a 
pond), except in cases where the source is directional. The 
compressions and decompressions associated with sound waves are 
detected as changes in pressure by aquatic life and man-made sound 
receptors such as hydrophones.
    Even in the absence of sound from the specified activity, the 
underwater environment is typically loud due to ambient sound. Ambient 
sound is defined as environmental background sound levels lacking a 
single source or point (Richardson et al., 1995), and the sound level 
of a region is defined by the total acoustical energy being generated 
by known and unknown sources. These sources may include physical (e.g., 
waves, earthquakes, ice, atmospheric sound), biological (e.g., sounds 
produced by marine mammals, fish, and invertebrates), and anthropogenic 
sound (e.g., vessels, dredging, aircraft, construction). A number of 
sources contribute to ambient sound, including the following 
(Richardson et al., 1995):
     Wind and waves: The complex interactions between wind and 
water surface, including processes such as breaking waves and wave-
induced bubble oscillations and cavitation, are a main source of 
naturally occurring ambient noise for frequencies between 200 Hz and 50 
kHz (Mitson, 1995). In general, ambient sound levels tend to increase 
with increasing wind speed and wave height. Surf noise becomes 
important near shore, with measurements collected at a distance of 8.5 
km from shore showing an increase of 10 dB in the 100 to 700 Hz band 
during heavy surf conditions.
     Precipitation: Sound from rain and hail impacting the 
water surface can become an important component of total noise at 
frequencies above 500 Hz, and possibly down to 100 Hz during quiet 
times.
     Biological: Marine mammals can contribute significantly to 
ambient noise levels, as can some fish and shrimp. The frequency band 
for biological contributions is from approximately 12 Hz to over 100 
kHz.
     Anthropogenic: Sources of ambient noise related to human 
activity include transportation (surface vessels and aircraft), 
dredging and construction, oil and gas drilling and production, seismic 
surveys, sonar, explosions, and ocean acoustic studies. Shipping noise 
typically dominates the total ambient noise for frequencies between 20 
and 300 Hz. In general, the frequencies of anthropogenic sounds are 
below 1 kHz and, if higher frequency sound levels are created, they 
attenuate rapidly (Richardson et al., 1995). Sound from identifiable 
anthropogenic sources other than the activity of interest (e.g., a 
passing vessel) is sometimes termed background sound, as opposed to 
ambient sound.
    The sum of the various natural and anthropogenic sound sources at 
any given location and time--which comprise ``ambient'' or 
``background'' sound--depends not only on the source levels (as 
determined by current weather conditions and levels of biological and 
shipping activity) but also on the ability of sound to propagate 
through the environment. In turn, sound propagation is dependent on the 
spatially and temporally varying properties of the water column and sea 
floor, and is frequency-dependent. As a result of the dependence on a 
large number of varying factors, ambient sound levels can be expected 
to vary widely over both coarse and fine spatial and temporal scales. 
Sound levels at a given frequency and location can vary by 10-20 dB 
from day to day (Richardson et al., 1995). The result is that, 
depending on the source type and its intensity, sound from the 
specified activity may be a negligible addition to the local 
environment or could form a distinctive signal that may affect marine 
mammals.
    The underwater acoustic environment in the Mayport turning basin is 
likely to be dominated by noise from day-to-day port and vessel 
activities. The basin is sheltered from most wave noise, but is a high-
use area for naval ships, tugboats, and security vessels. When 
underway, these sources can create noise between 20 Hz and 16 kHz 
(Lesage et al., 1999), with broadband noise levels up to 180 dB. While 
there are no current measurements of ambient noise levels in the 
turning basin, it is likely that levels within the basin periodically 
exceed the 120 dB threshold and, therefore, that the high levels of 
anthropogenic activity in the basin create an environment far different 
from quieter habitats where behavioral reactions to sounds around the 
120 dB threshold have been observed (e.g., Malme et al., 1984, 1988).
    In-water construction activities associated with the project would 
include impact pile driving and vibratory pile driving. The sounds 
produced by these activities fall into one of two general sound types: 
Pulsed and non-pulsed (defined in the following). The distinction 
between these two sound types is important because they have differing 
potential to cause physical effects, particularly with regard to 
hearing (e.g., Ward, 1997 in Southall et al., 2007). Please see

[[Page 75985]]

Southall et al., (2007) for an in-depth discussion of these concepts.
    Pulsed sound sources (e.g., explosions, gunshots, sonic booms, 
impact pile driving) produce signals that are brief (typically 
considered to be less than one second), broadband, atonal transients 
(ANSI, 1986; Harris, 1998; NIOSH, 1998; ISO, 2003; ANSI, 2005) and 
occur either as isolated events or repeated in some succession. Pulsed 
sounds are all characterized by a relatively rapid rise from ambient 
pressure to a maximal pressure value followed by a rapid decay period 
that may include a period of diminishing, oscillating maximal and 
minimal pressures, and generally have an increased capacity to induce 
physical injury as compared with sounds that lack these features.
    Non-pulsed sounds can be tonal, narrowband, or broadband, brief or 
prolonged, and may be either continuous or non-continuous (ANSI, 1995; 
NIOSH, 1998). Some of these non-pulsed sounds can be transient signals 
of short duration but without the essential properties of pulses (e.g., 
rapid rise time). Examples of non-pulsed sounds include those produced 
by vessels, aircraft, machinery operations such as drilling or 
dredging, vibratory pile driving, and active sonar systems (such as 
those used by the U.S. Navy). The duration of such sounds, as received 
at a distance, can be greatly extended in a highly reverberant 
environment.
    Impact hammers operate by repeatedly dropping a heavy piston onto a 
pile to drive the pile into the substrate. Sound generated by impact 
hammers is characterized by rapid rise times and high peak levels, a 
potentially injurious combination (Hastings and Popper, 2005). 
Vibratory hammers install piles by vibrating them and allowing the 
weight of the hammer to push them into the sediment. Vibratory hammers 
produce significantly less sound than impact hammers. Peak SPLs may be 
180 dB or greater, but are generally 10 to 20 dB lower than SPLs 
generated during impact pile driving of the same-sized pile (Oestman et 
al., 2009). Rise time is slower, reducing the probability and severity 
of injury, and sound energy is distributed over a greater amount of 
time (Nedwell and Edwards, 2002; Carlson et al., 2005).

Marine Mammal Hearing

    Hearing is the most important sensory modality for marine mammals, 
and exposure to sound can have deleterious effects. To appropriately 
assess these potential effects, it is necessary to understand the 
frequency ranges marine mammals are able to hear. Current data indicate 
that not all marine mammal species have equal hearing capabilities 
(e.g., Richardson et al., 1995; Wartzok and Ketten, 1999; Au and 
Hastings, 2008). To reflect this, Southall et al. (2007) recommended 
that marine mammals be divided into functional hearing groups based on 
measured or estimated hearing ranges on the basis of available 
behavioral data, audiograms derived using auditory evoked potential 
techniques, anatomical modeling, and other data. The lower and/or upper 
frequencies for some of these functional hearing groups have been 
modified from those designated by Southall et al. (2007). The 
functional groups and the associated frequencies are indicated below 
(note that these frequency ranges do not necessarily correspond to the 
range of best hearing, which varies by species):
     Low-frequency cetaceans (mysticetes): Functional hearing 
is estimated to occur between approximately 7 Hz and 25 kHz (extended 
from 22 kHz; Watkins, 1986; Au et al., 2006; Lucifredi and Stein, 2007; 
Ketten and Mountain, 2009; Tubelli et al., 2012);
     Mid-frequency cetaceans (larger toothed whales, beaked 
whales, and most delphinids): Functional hearing is estimated to occur 
between approximately 150 Hz and 160 kHz;
     High-frequency cetaceans (porpoises, river dolphins, and 
members of the genera Kogia and Cephalorhynchus; now considered to 
include two members of the genus Lagenorhynchus on the basis of recent 
echolocation data and genetic data [May-Collado and Agnarsson, 2006; 
Kyhn et al. 2009, 2010; Tougaard et al. 2010]): Functional hearing is 
estimated to occur between approximately 200 Hz and 180 kHz; and
     Pinnipeds in water: Functional hearing is estimated to 
occur between approximately 75 Hz to 100 kHz for Phocidae (true seals) 
and between 100 Hz and 40 kHz for Otariidae (eared seals), with the 
greatest sensitivity between approximately 700 Hz and 20 kHz. The 
pinniped functional hearing group was modified from Southall et al. 
(2007) on the basis of data indicating that phocid species have 
consistently demonstrated an extended frequency range of hearing 
compared to otariids, especially in the higher frequency range 
(Hemil[auml] et al., 2006; Kastelein et al., 2009; Reichmuth et al., 
2013).
    One cetacean species is expected to potentially be affected by the 
specified activity. Bottlenose dolphins are classified as mid-frequency 
cetaceans.

Acoustic Effects, Underwater

    Potential Effects of Pile Driving Sound--The effects of sounds from 
pile driving might result in one or more of the following: Temporary or 
permanent hearing impairment, non-auditory physical or physiological 
effects, behavioral disturbance, and masking (Richardson et al., 1995; 
Gordon et al., 2003; Nowacek et al., 2007; Southall et al., 2007). The 
effects of pile driving on marine mammals are dependent on several 
factors, including the size, type, and depth of the animal; the depth, 
intensity, and duration of the pile driving sound; the depth of the 
water column; the substrate of the habitat; the standoff distance 
between the pile and the animal; and the sound propagation properties 
of the environment. Impacts to marine mammals from pile driving 
activities are expected to result primarily from acoustic pathways. As 
such, the degree of effect is intrinsically related to the received 
level and duration of the sound exposure, which are in turn influenced 
by the distance between the animal and the source. The further away 
from the source, the less intense the exposure should be. The substrate 
and depth of the habitat affect the sound propagation properties of the 
environment. Shallow environments are typically more structurally 
complex, which leads to rapid sound attenuation. In addition, 
substrates that are soft (e.g., sand) would absorb or attenuate the 
sound more readily than hard substrates (e.g., rock) which may reflect 
the acoustic wave. Soft porous substrates would also likely require 
less time to drive the pile, and possibly less forceful equipment, 
which would ultimately decrease the intensity of the acoustic source.
    In the absence of mitigation, impacts to marine species would be 
expected to result from physiological and behavioral responses to both 
the type and strength of the acoustic signature (Viada et al., 2008). 
The type and severity of behavioral impacts are more difficult to 
define due to limited studies addressing the behavioral effects of 
impulsive sounds on marine mammals. Potential effects from impulsive 
sound sources can range in severity from effects such as behavioral 
disturbance or tactile perception to physical discomfort, slight injury 
of the internal organs and the auditory system, or mortality (Yelverton 
et al., 1973).
    Hearing Impairment and Other Physical Effects--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

[[Page 75986]]

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 not recoverable, or temporary 
(TTS), in which case the animal's hearing threshold would recover over 
time (Southall et al., 2007). Marine mammals depend on acoustic cues 
for vital biological functions, (e.g., orientation, communication, 
finding prey, avoiding predators); thus, TTS may result in reduced 
fitness in survival and reproduction. However, this depends on the 
frequency and duration of TTS, as well as the biological context in 
which it occurs. TTS of limited duration, occurring in a frequency 
range that does not coincide with that used for recognition of 
important acoustic cues, would have little to no effect on an animal's 
fitness. Repeated sound exposure that leads to TTS could cause PTS. PTS 
constitutes injury (direct auditory tissue effects), but TTS does not 
(Southall et al., 2007). The following subsections discuss in somewhat 
more detail the possibilities of TTS, PTS, and non-auditory physical 
effects.
    Temporary Threshold Shift--TTS is the mildest form of hearing 
impairment that can occur during exposure to a strong sound (Kryter, 
1985). While experiencing TTS, the hearing threshold rises, and a sound 
must be stronger in order to be heard. In terrestrial mammals, TTS can 
last from minutes or hours to days (in cases of strong TTS). For sound 
exposures at or somewhat above the TTS threshold, hearing sensitivity 
in both terrestrial and marine mammals recovers rapidly after exposure 
to the sound ends. Few data on sound levels and durations necessary to 
elicit mild TTS have been obtained for marine mammals, and none of the 
published data concern TTS elicited by exposure to multiple pulses of 
sound. Available data on TTS in marine mammals are summarized in 
Southall et al. (2007).
    Given the available data, the received level of a single pulse 
(with no frequency weighting) might need to be approximately 186 dB re 
1 [mu]Pa\2\-s (i.e., 186 dB sound exposure level [SEL] or approximately 
221-226 dB p-p [peak]) in order to produce brief, mild TTS. Exposure to 
several strong pulses that each have received levels near 190 dB rms 
(175-180 dB SEL) might result in cumulative exposure of approximately 
186 dB SEL and thus slight TTS in a small odontocete, assuming the TTS 
threshold is (to a first approximation) a function of the total 
received pulse energy.
    The above TTS information for odontocetes is derived from studies 
on the bottlenose dolphin and beluga whale (Delphinapterus leucas). 
There is no published TTS information for other species of cetaceans. 
However, preliminary evidence from a harbor porpoise exposed to pulsed 
sound suggests that its TTS threshold may have been lower (Lucke et 
al., 2009). As summarized above, data that are now available imply that 
TTS is unlikely to oc