**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 Northeast Pacific Ocean, October 2008**

**OCE \# 0454747**

**Principal Investigator:** Douglas Toomey

**Institution:** University of Oregon

**Project Title:** Collaborative Research: Testing Models of Magmatic
and Hydrothermal Segmentation: A 3-D Seismic Tomography Experiment at
the Endeavour Ridge

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* in the
northeast Pacific Ocean in October 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 Northeast Pacific Ocean, October 2008" (Report
#TA4597-1) (Attachment 1). The conclusions from the LGL report were used
to inform the Division of Ocean Sciences (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 Endeavour Tomography study (ETOMO), would include a seismic survey
that would provide data integral to advancing scientific understanding
of the sub-seafloor structure of volcanic and hydrothermal features that
form as a result of movements of the Earth's plates. The survey would
obtain information on the 3-D seismic structure of the crust and
top-most mantle along an 80-km-long section of the Juan de Fuca Ridge in
the Canadian Endeavour Marine Protected Area (MPA). This information
would define the distribution of magma beneath active volcanoes and the
nature of the reaction zone that connects magmatic and hydrothermal
systems. Such data would help us to better understand the transfer of
energy and mass between the solid earth and the oceans. Past studies
using manned submersibles and remotely piloted vehicles have mapped the
locations and characteristics of vent fields along this ridge segment.
The ETOMO study would extend that mapping beneath the seafloor and allow
us to understand the dynamics of these systems. This study would provide
basic subsurface constraints on the magmatic and hydrothermal processes
that lead to the hydrothermal vents which are the focus of the Canadian
MPA.

The ETOMO study would directly benefit one of the primary science nodes
of a cable-linked seafloor observatory in the Northeast Pacific Ocean,
which is being installed by the North-East Pacific Time-series Undersea
Networked Experiments (NEPTUNE) Canada (http://www.neptunecanada.ca).
More specifically, the information collected would improve knowledge of
the regional seismic velocity structure. This information would in turn
be used to obtain improved locations of earthquakes. Such information
would be vital to understanding plate tectonic processes and their
effects on earthquake occurrence and distribution. In addition, the
information would lead to a better understanding of the Endeavour
magmatic and hydrothermal systems, and thus improve interpretations of
time-series observations obtained by NEPTUNE Canada in and around the
Endeavour vent fields.

**Summary of Proposed Action and Alternatives**

The 2008 survey is proposed to be conducted \~250 southwest of Vancouver
Island, within the Canadian Endeavour MPA and the Exclusive Economic
Zone of Canada. A 36-airgun array, with a maximum discharge volume of
6600 in³ total, would be used as the energy source during the
experiment. The receiving system for the returning acoustic signals
would consist of 64 Ocean Bottom Seismometers (OBSs) which the
*Langseth* would also deploy and retrieve. A hydrophone streamer would
not be used to receive geophysical data during this survey. The planned
seismic survey would consist of \~1800 km of survey lines. All survey
efforts would take place in deep (\>1000 m) water.

[]{.mark}

One alternative to the proposed action would be to conduct the survey at
an alternative time. Constraints for vessel operations and availability
of equipment (including the vessel) and personnel would need to be
considered for alternative cruise times. Limitations on scheduling the
vessel include the additional research studies planned on the vessel for
2008 and beyond. Other national and international research activities
planned within the region also would need to be considered. Alternative
survey 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 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 advance scientific
understanding of the sub-seafloor structure of volcanic and hydrothermal
features that form as a result of movements of the Earth's plate 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 sub-seafloor structure of volcanic and hydrothermal
vent systems, plate tectonics, and earthquake occurrence and
distribution. 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 45-75 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. 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. Some behavioral disturbance is
expected, but this would be localized and short-term.

The proposed activity 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 7-17; and 59), mitigation measures that would be adopted,
include: ramp ups, minimum of one dedicated observer maintaining a
visual watch during all daytime airgun operations, two observers for 30
minutes before and during ramp-ups during the day and at night (and when
possible at other times), passive acoustic monitoring (PAM) during the
day and night when practicable, power downs (or if necessary shut downs)
when mammals or turtles are detected in or about to enter designated
exclusion zones, and additional special measures applicable to North
Pacific right whales.

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 fish habitat would be short term disturbance that could
lead to temporary relocation of pelagic fish species or their food.
Impacts of seismic sounds on birds are possible, although none are
expected to be significant to their populations. Impacts on benthic
invertebrates are unlikely. Considering the location of the planned
seismic survey, no significant impacts are expected on the availability
of marine mammals or fish for subsistence harvest.

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, page 75).

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 implementation of the
proposed activity will not have a significant impact on the environment.