**National Science Foundation**

**Geosciences Directorate**

**Division of Ocean Sciences**

**Arlington, Virginia**

**DRAFT ENVIRONMENTAL ASSESSMENT (DEA)**

**PURSUANT TO THE NATIONAL ENVIRONMENTAL POLICY ACT,**

**42 U.S.C. 4321, *et seq.***

**Marine Seismic Survey in the Gulf of Alaska (GOA), September 2008**

**EAR #0408584**

**Principal Investigator:** Sean S. Gulick

**Institution:** University of Texas at Austin, Institute for Geophysics
(UTIG)

**Project Title:** COLLABORATIVE RESEARCH: ST. Elias Erosion/tectonics
Project (STEEP)

This constitutes a draft environmental assessment (DEA) by the National
Science Foundation (NSF) for a marine seismic survey proposed to be
conducted on board the research vessel (R/V) *Marcus G. Langseth,*
operated by Columbia University's Lamont-Doherty Earth Observatory
(LDEO), in the GOA during September 2008. This DEA is based, in part, on
an Environmental Assessment prepared by LGL Limited, environmental
research associates (LGL) on behalf of NSF, entitled, "Environmental
Assessment of a Marine Geophysical Survey by the R/V *Marcus G.
Langseth* in the Gulf of Alaska, September 2008" (Report #TA4412-1)
(Attachment 1). The conclusions from the LGL report were used to inform
OCE management of potential environmental impacts of the 2008 cruise.
After the LGL report was fully and independently reviewed by OCE
management, OCE management concurred with the report's findings.
Accordingly, the LGL report is incorporated into this DEA by reference
and fully adopted as if fully set forth herein.

**Project Objectives and Context**

The proposed seismic survey will examine crustal structure, fault
patterns, and tectonic-climate geohistory of the area. The program will
investigate the interplay of climate and tectonics onshore and offshore
in an area that includes the world's largest strikeslip earthquakes
(Magnitude 8.0 Denali Event), largest earthquake caused uplift (14.4 m
in 1962), largest area of seismic uplift (during the 1962 event),
highest tsunami (over 200 m in Latoya Bay in 1958), largest temperate
glaciers (the Malaspina and Bering Glaciers), and some of the highest
sedimentation rates (over 1 m per year in some places). Nowhere else on
the planet are tectonics and climate interacting to create this
combination of mountain building, glacial erosion, strike-slip
(California style), and subduction (Japan style) earthquakes.

While affecting only a small local population, natural seismic activity
in the Gulf of Alaska (GOA) could influence the whole of the North
Pacific basin which includes many large population centers. Alaska is
being directly affected by modern climate change, and new evidence
suggests that, in fact, as climate changes, tectonics respond and vice
versa. This interplay could be fundamental to the way the Earth works as
a system, and by examining this interplay since the onset of glaciers,
the intention of the STEEP program is to examine the feedbacks that
drive the system.

The STEEP program is 5 years in length and includes scientists from over
10 universities. The study represents the most comprehensive study of
tectonic and climate interactions ever undertaken in a single project.
The offshore seismic component is a keystone for the experiment. The
data obtained from the seismic survey will be used to determine the
history of tectonic-climate interplay, as well as the nature of the
Yakutat plate that is causing all of the deformation in southern Alaska,
built the Saint Elias Mountains, and started the aggressive glaciation
that continues today.

**Summary of Proposed Action and Alternatives**

The proposed action is a seismic survey, providing essential data in
support of the above described research that would be conducted in the
GOA, in the territorial waters and Exclusive Economic Zone (EEZ) of the
United States. The R/V *Marcus G. Langseth* would deploy as an energy
source an array of up to 36 airguns, with a total discharge volume of
6600 in³. The receiving system for the returning acoustic signals would
consist of a towed hydrophone streamer and/or Ocean Bottom Seismometers
(OBSs).

One alternative to the proposed action would be to conduct the survey at
an alternative time. The proposed time for the STEEP cruise, however, is
the most suitable time logistically for the R/V *Marcus G.* *Langseth*
and the participating scientists as well as the additional research
studies planned on the vessel for 2008 and beyond. Within the weather
window that will allow vessel operations, alternative times offer
minimal advantages or disadvantages in this location.

Another alternative to conducting the proposed activities would be the
"No Action" alternative, i.e., do not issue an IHA and do not conduct
the operations. If the planned research were not conducted, the "No
Action" alternative would result in no disturbance to marine mammals
attributable to the proposed activities, and no environmental impacts of
other types. The seismic data from the proposed seismic survey to
examine crustal structure, fault patterns, and tectonic-climate
geohistory of the area would not be available for use and the project
objectives as described above would not be met. It is anticipated that
the data collected from a survey such as that proposed will be critical
in furthering the understanding of Earth processes, climate change, and
phenomena such as tsunamis and earthquakes (strike-slip and subduction)
that can have catastrophic impacts on society. The "No Action"
alternative would result in a lost opportunity to obtain important
scientific data and knowledge relevant to a number of research fields
and to society in general. The institutions, investigators, students,
and technicians involved would lose collection of new data, thus halting
support of the greater effort to process and interpret these data, and
introduce new results into the greater scientific community. Loss of NSF
support often represents a significant negative impact to the academic
infrastructure.

**Summary of environmental consequences**

The potential effects of sounds from airguns are described in detail in
Attachment 1 (pages 49-83 and Appendices B-E) and might include one or
more of the following: tolerance, masking of natural sounds, behavioral
disturbance, and at least in theory, temporary or permanent hearing
impairment, or non-auditory physical or physiological effects. With the
possible exception of some cases of temporary threshold shift in harbor
seals, it is unlikely that the project would result in any cases of
temporary or especially permanent hearing impairment, or any significant
nonauditory physical or physiological effects.

The proposed activity (seismic survey in the Gulf of Alaska) would
include a mitigation program to minimize impacts on marine mammals that
may be present during the conduct of the research to a level of
insignificance. As detailed in Attachment 1 (pages 7-16; and 63),
mitigation measures that would be adopted, include: airgun ramp ups;
minimum of one dedicated observer maintaining a visual watch during all
daytime airgun operations; two observers 30 minutes before and during
day and night ramp ups (and when possible at other times); passive
acoustic monitoring (PAM) via towed hydrophones during both day and
night (when practicable) activities; power downs (or if necessary shut
downs) when marine mammals or sea turtles are detected in or about to
enter designated exclusion zones; shut downs if North Pacific right
whales are sighted at any distance from the source vessel (given their
special status); avoidance of close approaches to Steller sea lion
rookeries and haulouts; and, avoidance of concentrations of humpback
whales, fin whales, and sea otters.

With the planned monitoring and mitigation measures, unavoidable impacts
to each species of marine mammal and turtle that could be encountered
are expected to be limited to short-term, localized changes in behavior
(such as temporary masking of natural sounds) and distribution near the
seismic vessel. At most, effects on marine mammals may be interpreted as
falling within the U.S. Marine Mammal Protection Act (MMPA) definition
of "Level B Harassment" for those species managed by the National Marine
Fisheries Service. No long-term or significant effects are expected on
individual marine mammals, sea turtles, or the populations to which they
belong, or on their habitats.

The proposed project would have little impact on fish resources, and the
only effect on EFH would be short term disturbance that could lead to
temporary relocation of EFH species or their food. Impacts of seismic
sounds on birds are possible, although none are expected to be
significant to their populations.

Considering the limited time and locations of the planned seismic
survey, no significant impacts are expected on the availability of
marine mammals or fish for the subsistence harvest. The potential for
negative impacts on subsistence harvesting and commercial fisheries
would be minimized by avoiding seismic operations in areas where those
activities would be occurring at the time of the survey. Also, villages
near the planned project area would be consulted to identify and avoid
areas of potential conflict.

As marine mammals are expected to be found throughout the proposed study
area and throughout the time period during which the project may occur,
no significant benefits would be gained from the alternative to conduct
the survey at a different time (see Attachment 1, pages 82-83).

The "no action" alternative would not have any environmental
consequences; although it would preclude important scientific research
from going forward.

**Conclusions**

NSF has reviewed and concurs with the conclusions of the LGL
Environmental Assessment (Attachment 1) that supports the conclusion
that implementation of the proposed activity will not have a significant
impact on the environment.