National Science Foundation.
Notice of availability of a draft Environmental Assessment for proposed activities in the Eastern Tropical Pacific Ocean.
The National Science Foundation (NSF) gives notice of the availability of a draft Environmental Assessment (EA) for proposed activities in the Eastern Tropical Pacific Ocean.
The Division of Ocean Sciences in the Directorate for Geosciences (GEO/OCE) has prepared a draft Environmental Assessment for a pair of marine geophysical surveys by the Research Vessel Marcus G Langseth in the Eastern Tropical Pacific Ocean, in international waters (2000-5000 meters depth) between 5° S and 11° N, along ~105° W during September-December 2007. The draft Environmental Assessment is available for public review for a 30-day period.
Comments must be submitted on or before July 6, 2007.
Copies of the draft Environmental Assessment are available upon request from: Dr. William Lang, National Science Foundation, Division Start Printed Page 31352of 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_ETP_2007_EA.pdf.End Preamble Start Supplemental Information
Lamont-Doherty Earth Observatory (LDEO), with research funding from the NSF, plans to conduct two marine seismic surveys in the Eastern Tropical Pacific Ocean (ETP) during 2007. The research programs will take place in international waters of the ETP at least 890 km from any coast. The surveys will use a towed airgun array consisting of up to 27 operating airguns with a maximum discharge volume of 4950 in3. The studies will take place in offshore waters >2000 m deep.
The first survey will start in September 2007 and will obtain seismic reflection images of the internal structure of the magmatic-hydrothermal system at the fast-spreading mid-ocean ridge of the East Pacific Rise (EPR). The seismic data from the EPR survey will be used to advance our understanding of the linkages between the fundamental process of crustal creation at the mid-ocean ridge and the biological systems that thrive in the absence of sunlight at deep sea volcanoes. The survey will allow the characterization of the fundamental heat source driving the seafloor hydrothermalism in the EPR, by examining the subsurface magma system. It will also provide an understanding of the relationships between the temporal variations in subsurface magma systems and highly transient phenomena observed at the seafloor like faulting, volcanism, and hydrothermal venting. Hydrothermal systems are of great interest in that they may be linked to the origin of life in early Earth history.
The second survey is expected to take place from early November through December 2007. It will examine two important types of seismic behavior of the Quebrada, Discovery, and Gofar fault systems (QDG) to understand better the behavior of earthquakes and faults in general. Oceanic transform faults, such as the QDG, are the most poorly studied of the various types of plate boundaries. The QDG survey will examine the seismogenic properties that make oceanic transforms unique, including abundant foreshocks before large earthquakes, slow ruptures, and large variations in fault seismic coupling. The two main questions to be addressed by the study are: (1) Do large and small earthquakes nucleate in the same way, or is there some kind of fault preparation process before large events, and (2) why do some faults remain locked for decades to centuries between large earthquakes while others creep aseismically and never have a large event? Refraction images of the material properties in both fault zones will provide important information about the physics of faulting and the earthquake process.
The first survey (EPR) is a multichannel seimic (MCS) reflection survey in a 3D configuration. The survey will consist of two racetrack configurations with a total of 36 loops that will cover an area of ~28 × 28 km. The Langseth will deploy a 36-airgun array as an energy source. However, two identical two-stirring sources will be firing alternately, so that no more than 18 airguns will be firing at any time. The maximum discharge volume will be 3300 in3. The Langseth will also tow the receiving system, which consists of four 6-km hydrophone streamers; each streamer will be located 100 m from the adjacent streamer. The second study (QDG) will consist of a refraction survey done in a 2D configuration. It will consist of two north-south lines, each ~122 km in length, each to be surveyed twice. If there is time, two 25-km west-east lines will also be surveyed, and one of the north-south lines will be resurveyed. With the contingency surveys, the study will consist of a total of 654 km of survey lines, including turns. The Langseth will deploy a 36-airgun array as an energy source. However, no more than 27 airguns will be fired at any time. The maximum discharge volume will be 4950 in3. A single 8-km streamer will be deployed. The Langseth will also deploy 40 long-term OBSs, deployed over a 50-km wide spread. The long-term OBSs will be recovered 1 year after deployment. Another 8-10 short-term OBSs will be deployed on each line, which will be retrieved after the seismic surveys are completed.
LDEO has applied for the issuance of an Incidental Harrassment 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 the 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 cetaceans and sea turtles occur in the Eastern Tropical Pacific Ocean. Several of the cetacean species are listed as endangered under the U.S. Endangered Species Act (ESA), including the humpback, sei, fin, blue, and sperm whales. Sea turtles that are known to occur in the ETP include the endangered leatherback, green, olive ridley, and hawksbill turtle, and the threatened loggerhead turtle.
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 cause 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 minutes before start up. A passive acoustic monitoring (PAM) array will be monitored 24 hours per day while at the survey area during airgun operations and 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 Start Printed Page 31353distribution 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 two Marine Geophysical Surveys by the Marcus G. Langseth in the Eastern Tropical Pacific, 2007,” 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/MGL ETP 2007 EA.pdf. The NSF invites interested members of the public to provide written comments on this draft EA.Start Signature
Dated: May 31, 2007.
Dr. Alexander Shor,
Program Director, Oceanographic Instrumentation and Technical Services, Division of Ocean Sciences, National Science Foundation.
[FR Doc. 07-2809 Filed 6-5-07; 8:45 am]
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