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Soundings Archive

BOEM Publishes Data on Effectiveness of Seismic Mitigation Measures
Since 2002, the U.S. federal government Agency now known as Bureau of Ocean Energy Management, Regulation and Enforcement (BOEM) has implemented a seismic survey mitigation measures Notice to Lessees (NTL). This initial NTL (2002-G07) has subsequently been updated (2003-G08; 2004-G01; 2007-G02) and expanded to include a variety of mitigations and reporting requirements. These measures apply to all on-lease oil and gas seismic surveys conducted in the Gulf of Mexico. Seismic operators in the GOM are required to submit reports electronically to BOEM. Reporting requirements include an observer effort report, survey reports and sightings report.

As part of the original Biological Opinion that resulted in the seismic survey observer program, the U.S. National Marine Fisheries Service (NMFS) also requires that an annual report be submitted documenting all sightings of sperm whales and sea turtles, which are the species currently listed under the Endangered Species Act (ESA) that are likely to be sighted during oil and gas seismic operations in the GOM.

As a result, BOEM now has considerable data from the observer program and is in a position to evaluate existing seismic mitigations and their effectiveness. These data are contained in a BOEM report entitled "Seismic Survey Mitigation Measures and Marine Mammal Observer Reports (GM-08-02)." This report is available online at .

These data will be used by BOEM and NMFS during the Marine Mammal Protection Act (MMPA) rulemaking process for oil and gas seismic takes in the GOM. These data will also be used by BOEM and NMFS for MMPA and ESA consultations.

This is an important report, and it is data intensive. Consequently, the report's data- rich Executive Summary is quoted in its entirety below:


  • Mitigation observation data were collected during seismic survey operations in the Gulf of Mexico (GOM), United States of America (USA) between December 2002 and December 2008 under Notice to Lessees (NTL) 2007-G02 and earlier versions. The required submissions included observer effort, record of operations and sighting report data forms within each biweekly report.

  • A total of 1,440 bi-weekly reports were received by the Bureau of Ocean Energy Management (BOEM), formerly the Minerals Management Service (MMS), for seismic surveys; a total of 194,273 visual survey hours were recorded.

  • Visual observations yielded 3,963 complete sighting records; approximately 28,000 individual animals were represented in the records.

  • Cetaceans comprised 3,335 (85%) of these records with 20 species identified. Sea turtles comprised the remaining 579 (15%) records with five species identified. The most common cetacean encountered was the sperm whale, Physeter Macrocephalus (N=1,136 records); the most common small cetacean identified was the pantropical spotted dolphin (Stenella attenuata), (N=740 records).

  • There were 32,939 ramp-ups recorded within all bimonthly reports. Of these records 65% were fully complete or nearly complete so that ramp-up activity and compliance were clearly discernible. Of the ramp-ups recorded, 90% were between 20 and 40 minutes in duration, as required by the NTL.

  • Of the daytime ramp-up records 86% had data complete enough to discern compliance with the pre-firing survey requirement. Only 3% of the pre-firing surveys were less than the required 30 minute duration.

  • There were 32 delays in ramp-ups due to the presence of protected species in the exclusion zone during the 30 minutes immediately prior to ramp-up. Of these delays, 24 (75%) were due to dolphins, four (12.5%) due to sea turtles, and four (12.5%) due to sperm whales.

  • There was a total of 18.5 hours of down time attributed to ramp-up delays.

  • There were 144 occurrences of whales visually detected in the exclusion zone that resulted in a shutdown of airguns. Of the required 144 shutdown events, 139 (97%) were due to sperm whales.

  • The average downtime resulting from shutdowns was 58 minutes and there was a total of 125.74 hours of down time attributed to shutdowns.

  • Shut down frequency for sperm whales was 0.71 shutdowns per 1,000 hours of observation, resulting in an estimated 1 shutdown for every 1,500 hours (or roughly 125 days) of daylight survey operations, assuming observations are conducted during all daylight hours regardless of gun operations.

  • The mean dolphin sighting frequency decreased 9% during airgun ramp-up procedures when compared to airgun silence. However, dolphin sighting frequency during minimum source firing sightings was equal to that during gunsilence. Dolphin sighting frequency when airguns were at full power increased 14% when compared to silent mode.

  • The minimum distance of dolphins to airguns increases from silent, to ramp-up, to mitigation, and full power. At full power, the mean closest approach of dolphins to airgun arrays was 90% further away than during silent status."
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