National Science Foundation.
Notice of availability of a draft Environmental Assessment for proposed activities in the Eastern Pacific Ocean and Caribbean Sea near Central America.
The National Science Foundation (NSF) gives notice of the availability of a draft Environmental Assessment (EA) for proposed activities in the Eastern Pacific Ocean and Caribbean Sea near Central America.
The Division of Ocean Sciences in the Directorate for Geosciences (GEO/OCE) has prepared a draft Environmental Assessment for a marine geophysical survey by the Research Vessel Marcus G Langseth in the Eastern Pacific Ocean and Caribbean Sea near Central America, in the Exclusive Economic Zones of Costa Rica and Nicaragua (water depths from <100 meters to >2500 meters) during January-March 2008, The draft Environmental Assessment is available for public review for a 30-day period.
Comments must be submitted on or before October 1, 2007.
Copies of the draft Environmental Assessment are available upon request from: Dr. William Lang, National Science Foundation, Division of Ocean Sciences, 4201 Wilson Blvd., Suite 725, Arlington, VA 22230. Telephone: (703) 292-7857. The draft is also available on the agency's Web site at: http://www.nsf.gov/geo/oce/pubs/MGL_Central_America_2008_EA.pdf.End Preamble Start Supplemental Information
Lamont-Doherty Earth Observatory (LDEO), with research funding from the NSF, plans to conduct a marine seismic survey in the Eastern Pacific Ocean and Caribbean Sea near Central America during 2008. The research program will take place in the Exclusive Economic Zones of Costa Rica and Nicaragua. The surveys will use a towed airgun array consisting of up to 36 operating airguns with a maximum discharge volume of ~6600 in3. They will take place in waters from <100 meters to >2500 meters deep.
LDEO plans to conduct this seismic survey as part of the “Subduction Factory,” or “SubFac” initiative of NSF's MARGINS program. The SubFac initiative will determine the inputs, outputs, and controlling processes of subduction zone systems by obtaining seismic measurements of magma flux, are composition, and lower-plate serpentinization at the Central American Focus Site. Subduction zones, which mark sites of convective downwelling of the Earth's lithosphere, exist at convergent plate boundaries where one plate of oceanic lithosphere converges with another plate and sinks below into the mantle. It is at these subduction zones that the oceanic crust and associated sediments are recycled into the deep mantle. Although this mixing of the Earth's crustal and oceanic materials produces ore deposits and new continental crust in the long term, the immediate result is geological activity often expressed as deep, very intense earthquakes and extensive volcanism.
The seismic survey will investigate the volcanic are, back are, and downgoing plate in the Costa Rican portion of the Central American Focus Site. The study focuses on the central Costa Rican segment of the are, the site of important transitions in lava chemistry, because the narrow isthmus ~150 km or 93 mi wide) is well-suited for detailed seismic imaging using onshore-offshore techniques. A systemic understanding of subduction must include a thorough knowledge of the volcanic are, which in turn is essential in understanding the geochemical recycling processes of the Central American SubFac.
To investigate the Central American SubFac, seismic survey transects are proposed across the isthmus in Costa Rica, along the Costa Rican arc and back-arc, the outer rise of the Cocos Plate, and the Nicaragua Rise. The cross-arc transect will involve use of seismic sources in both the Pacific and Caribbean. To understand arc-building processes, the delineation of lateral heterogeneity in crustal thickness and velocity at scales of tens of kilometers is required, both across and along-arc. In order to achieve this, the study will acquire (1) A double-side, onshore-offshore cross-arc profile, (2) an along-arc refraction line, (3) an array of seismometers in the arc to record all onshore and offshore shots and to allow 3-dimensional (3D) tomography, and (4) a refraction survey across the outer rise of the downgoing Cocos Plate.
The marine program will consist of ~2149 km of unique survey lines—753 km in the Caribbean and 1396 km in the Pacific. With the exception of two lines located in shallow to intermediate-depth water, all lines will be shot twice, once at a ~50-m (20-s) shot spacing for multichannel seismic (MCS) data and once at a ~200-m (80-s) shot spacing for ocean bottom seismometer (OBS) refraction data, for a total of ~3980 km of survey lines. There will be additional operations associated with equipment testing, startup, line changes, and repeat coverage of any areas where initial data quality is sub-standard.
LDEO has applied for the issuance of an Incidental Harassment Authorization (IHA) from the National Marine Fisheries Service (NMFS) to authorize the incidental harassment of small numbers of marine mammals during the seismic survey. The information in this Environmental Assessment supports the IHA permit application process, provides information on marine species not covered by the IHA, and addresses Start Printed Page 50413the requirements of Executive Order 12114, “Environmental Effects Abroad of Major Federal Actions”. Alternatives addressed in this EA consist of a corresponding seismic survey at a different time, along with issuance of an associated IHA; and the no action alternative, with no IHA and no seismic survey.
Numerous species of marine mammals occur off Central America. Several of the cetacean species are listed as endangered under the U.S. Endangered Species Act (ESA), including humpback, sei, fin, blue, and sperm whales. In addition, the endangered West Indian manatee is known to occur in shallow waters along the Caribbean coast of Central America. Sea turtle species known to occur in Central America include the endangered leatherback and hawksbill turtles, the threatened loggerhead turtle, the green turtle (considered endangered in the breeding colony of Florida and the Pacific coast of Mexico and threatened elsewhere), and the olive ridley turtle (designated as endangered in the breeding colony of the Pacific coast of Mexico and threatened elsewhere). The Kemp's ridley turtle may also occur in the Caribbean.
The potential impacts of the seismic surveys would be primarily a result of the operation of airguns, although a multi-beam sonar and a sub-bottom profiler will also be operated. Impacts may include increased marine noise and resultant avoidance behavior by marine mammals, sea turtles, and fish; and other forms of disturbance. The operations of the project vessel during the study would also a minor increase in the amount of vessel traffic. An integral part of the planned survey is a monitoring and mitigation program designed to minimize the impacts of the proposed activities on marine mammals and sea turtles that may be present during the proposed research, and to document the nature and extent of any effects. Injurious impacts to marine mammals and sea turtles have not been proven to occur near airgun arrays; however the planned monitoring and mitigation measures would minimize the possibility of such effects should they otherwise occur.
Protection measures designed to mitigate the potential environmental impacts will include the following: A minimum of one dedicated marine mammal observer maintaining a visual watch during all daytime airgun operations, and two observers for 30 min before start up. A passive acoustic monitoring (PAM) array will be monitored 24 h per day while at the survey area during airgun operations and during most times when the Langseth is underway while the airguns are not operating. The use of ramp-up, as well as implementation of power-down or shut-down procedures when animals approach a designated exclusion zone (EZ) are also important mitigation measures. LDEO and its contractors are committed to apply those measures in order to minimize disturbance of marine mammals and sea turtles, and also to minimize the risk of injuries or of other environmental impacts.
With the planned monitoring and mitigation measures, unavoidable impacts to each of the species of marine mammal that might be encountered are expected to be limited to short-term localized changes in behavior and distribution near the seismic vessel. At most, such effects may be interpreted as falling within the Marine Mammal Protection Act (MMPA) definition of “Level B Harassment” for those species managed by NMFS. No long-term or significant effects are expected on individual marine mammals, or the populations to which they belong, or their habitats. The agency is currently consulting with the NMFS regarding species within their jurisdiction potentially affected by this proposed activity.
Copies of the draft EA, titled “Environmental Assessment of a Marine Geophysical Survey by the R/V Marcus G. Langseth off Central America, January-March 2008,” are available upon request from: Dr. William Lang, National Science Foundation, Division of Ocean Sciences, 4201 Wilson Blvd., Suite 725, Arlington, VA 22230. Telephone: (703) 292-7857 or at the agency's Web site at: http://www.nsf.gov/geo/oce/pubs/MGI_Central_America_2008_EA.pdf. The NSF invites interested members of the public to provide written comments on this draft EA.Start Signature
Dated: August 27, 2007.
Dr. Alexander Shor,
Program Director, Oceanographic Instrumentation and Technical Services, Division of Ocean Sciences, National Science Foundation.
[FR Doc. 07-4267 Filed 8-30-07; 8:45 am]
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