**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 Santa Barbara Channel, November 2008**

**ODP #0751807**

**Principal Investigator:** Craig Nicholson

**Institution:** UCSB

**Project Title:** Collaborative Research: A Test for Extending the
High-Resolution Climate Record Back to 1.2 Ma - Investigating the
Mid-Pleistocene Climate Transition in Santa Barbara Basin

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) *Melville,* operated by
University of California's Scripps Institution of Oceanography (SIO), in
the Santa Barbara Channel during November 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
*Melville* in the Santa Barbara Channel, November 2008" (Report
#TA4643-1) (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 would test the feasibility of extending the
remarkable high-resolution paleoclimate record from Santa Barbara Basin
from \~700,000 years ago back to \~1.2 million years ago. This would be
accomplished by conducting detailed 3D modeling of the structure and
outcrop stratigraphy of the northern shelf to locate optimal core sites,
and by conducting high-resolution seismic reflection site surveys,
piston coring, and core analyses of both the northern shelf and
mid-channel area. A similar seismic and coring expedition in 2005
verified the presence of this remarkable paleoclimate record back to
\~700,000 years ago in the mid-channel region. An integrated seismic
data acquisition and coring cruise would be conducted to (1) acquire
piston core samples of older marine sediments that are now exposed at
the seafloor to test the suitability of these older deep basin sediments
to provide a high-quality paleoclimate record, and (2) conduct
high-resolution multi-channel seismic (MCS) surveys of the coring sites
to place the results from the core analyses in a wider basin context,
and to identify subsequent op­timal and safe coring strategies suitable
for recovering a continuous paleoclimate record from the shallow marine
sediments in Santa Barbara Basin in the future as part of the Integrated
Ocean Drilling Program (IODP). The acquisition of both seismic and
coring data would also help tremendously in terms of providing critical
sub-seafloor geologic and geophysical information needed to conduct
additional coastal environmental and hazard studies in the Santa Barbara
Channel area where a large and growing coastal population is currently
at risk. In addition, the data would contribute to a better
understanding of the processes of global climate change. USGS would
provide scientific personnel and equipment in support of this cruise.

**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
Santa Barbara Channel, in the territorial waters of the United States,
partly in California state waters. The survey would involve one source
vessel, the R/V *Melville*. Seismic sources to be deployed by the R/V
*Melville* would vary with water depth. At two shallow-water sites that
cross into California state waters, a 1.5 kiloJoule (kJ)
electromechanical boomer or a 2 kJ electric sparker system would be
used, depending on water depth and seafloor conditions, and depending on
which source provides the highest resolution and best sub-seafloor
signal penetration. In general, the boomer source likely would be
preferred. At three deeper-water sites outside state waters, a small (25
to 45 cubic inch) GI airgun would be used. The receiving system for the
returning acoustic signals would consist of a 72 channel, 450 meter long
towed hydrophone streamer. As the boomer, sparker, or GI airgun are
towed along the survey lines, the hydrophone streamer would receive the
returning acoustic signals and transfer the data to the on-board
processing system.

One alternative to the proposed action would be to conduct the survey at
an alternative time. The proposed time for this cruise, however, is the
most suitable time logistically for the R/V *Melville,* the
participating scientists, necessary equipment, as well as the additional
research studies planned on the vessel for 2008 and beyond. Marine
mammals are expected to be found throughout the proposed study area and
throughout the time period during which the project may occur.

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 collected from the proposed seismic survey
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 would be critical in furthering the
understanding of our paleoclimatic record, climate change, and coastal
environmental and hazard studies. 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.
The "No Action" alternative could also, in some circumstances, result in
significant delay of other geophysical studies that are planned by SIO
for 2008 and beyond, depending on the timing of the decision, and would
result in a cancellation of an important aspect of the IODP.

**Summary of environmental consequences**

The potential effects of sounds from airguns are described in detail in
Attachment 1 (pages 42-71 and Appendices A-D) 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 and perhaps some other 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.

[]{.mark}

The proposed activity would include a monitoring and 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 7-12; and 56), mitigation measures that would be
adopted would include (1) vessel speed or course alteration, provid­ed
that doing so would not compromise operational safety requirements, (2)
GI airgun or boomer shut down within calculated exclusion zones, (3)
minimizing approach to slopes and submarine canyons, if possible,
because of sensitivity of beaked whales, and (4) shut down at any range
in the unlikely event that a North Pacific right whale or a
concentration of sea otters is sighted. The fact that the GI airgun, as
a result of its design, directs the majority of the energy downward, and
less energy laterally, is also an inherent miti­gation measure. Two other
standard mitigation measures--- airgun array power down and airgun array
ramp up---are not possible because only one, low-volume GI airgun would
be used for the surveys. There would be a minimum of one dedicated
observer maintain­ing a visual watch during all daytime airgun operations
(and when possible at other times) and shut downs when mammals or
turtles are detected in or about to enter designated exclusion zones.

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.

A number of marine mammal species are year-round residents in the SCB,
so altering the timing of the proposed project likely would result in no
net benefits for those species. Other marine mammal species (e.g., the
gray whale and northern elephant seal) are migratory, and are absent
from the SBC at the time of the proposed survey. Therefore, postponing
the proposed project to a later time in the year could result in higher
numbers of migratory species in the SBC during the proposed survey (see
Attachment 1, page 70).

The "No Action" alternative would not have any environmental
consequences; although it would preclude important scientific research
from going forward (see Attachment 1, page 71).

**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 would not have a
significant impact on the environment.