New mitigation measures ordered by the US Minerals Management Service, effective Aug. 22, to protect sperm whales from underwater noise damaging to them will raise the cost of seismic exploration in the Gulf of Mexico.
But it won't be nearly as costly as the original proposal contained in a biological opinion by the fisheries division of the US National Oceanic and Atmospheric Administration (NOAA) that threatened to shut down seismic exploration at night and during other periods of limited visibility, said Gordon C. "Chip" Gill, president of the International Association of Geophysical Contractors, Houston.
IAGC officials worked fast to soften the potential impact of new mitigation measures introduced by MMS in mid-July through a final notice of federal Lease Sale 184 for the western gulf (OGJ, Aug. 26, 2002, p. 32).
Gill claimed the biological opinion issued by NOAA in conjunction with the sale contains "a number of fundamental flaws that have resulted in some inappropriate and unwise stipulations."
Protection concepts
In an Aug. 2 letter to Dr. William S. Hogarth, assistant administrator for fisheries at NOAA, Gill said, "The stipulations would result in some significant changes in the operation of seismic activities in the (waters of the outer continental shelf) that we believe are unwarranted and unnecessary.
"As a matter of fact, we believe some of the requirements could actually result in greater impacts on marine mammals."
IAGC officials claimed NOAA's original proposal, based on a noise level of 180 db in 200 m of water or more, would set "an unwise and needlessly restrictive precedent" with an impact zone "much larger than needed in order to protect sperm whales."
That proposal was worded so vaguely, with no references to frequencies or other parameters, they said, that the required exclusion zone for whales could have been interpreted as extending as much as a 5 mile radius around an airgun source.
Such a large area would have been physically impossible to monitor, IAGC officials claimed.
However, the notice issued by MMS limits the exclusion zone to a much smaller radius of 500 m "at and below the sea surface" surrounding the center of a seismic airgun array and within the immediate vicinity of the survey vessel.
"That's the same requirement as in the North Sea," Gill said. "We know we can successfully monitor an area of that size."
The MMS notice also requires seismic crews to ramp up initial firing of their airguns, starting with a single unit of the lowest power and increasing at a rate of 6 db every 5 min until the entire array is operating at the desired intensity for a survey.
That, too, is normal procedure for marine seismic crews so as to "push" out of the adjacent area any marine animals that might be sensitive to underwater noise, Gill said. After all, he said, "No one wants to get a whale caught in their gear" of geophone streamers strung out some 8 km behind a seismic vessel.
Airgun ramp-up
Seismic workers must visually monitor the exclusion zone and adjacent waters for at least 30 min to make sure no sperm whale is present before starting to ramp up their array of airguns, said MMS officials.
But once the airgun array is activated, workers may continue to work at night or in adverse weather conditions that limit visibility as long as the airguns keep generating a minimum 160 db of sound, on the theory that keeping a noise source in the water will continue to keep sperm whales out of the affected area.
The original NOAA proposal would have forced seismic crews to cease operations anytime visibility conditions deteriorated to the point that visual monitoring of the affected area was impossible (OGJ, Sept. 13, 1999, p. 105).
Forcing such shutdowns, with subsequent ramp-up periods as visual conditions improved, could double the cost of marine seismic surveys by doubling the time it takes to collect seismic data, in a "worst-case scenario," said Gill. "Assuming we're shut down at night, we can only be shooting half the time."
Moreover, he said, forcing one seismic crew to shut down would wreck the "time shares" coordination required for multiple seismic crews to survey the same area for different clients, with one crew shooting its survey while another crew is making its turn and aligning its arrays of airguns and geophones for its next pass through that area.
Crew observers
In another victory for IAGC, MMS officials ruled that seismic contractors may delegate seismic crew members to do visual monitoring for whales "until trained visual observers can replace them.
"All seismic vessels must have trained observers for visual monitoring requirements within 2 months of the effective date (Aug. 22) of this NTL (notice to lessees and operators)."
Furthermore, MMS stipulated that seismic crew members could qualify as trained visual observers if they successfully complete a training program approved by NOAA. "Originally, NOAA Fisheries proposed to put its own people on our boats as observers," said Gill.
"We'll have to add personnel, with observers probably working 4-hour shifts."
(A longer version of this story is searchable at www.ogjonline.com)
