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Petroleum News: MMS issues EA for seismic programs

Environmental assessment for Chukchi, Beaufort Sea stipulates protections for wildlife, requires a conflict avoidance agreement

By Alan Bailey

The U.S. Minerals Management Service has published its final programmatic environmental assessment (or PEA) for seismic surveys in the Chukchi and Beaufort seas. The agency has prepared the PEA in response to a heightened level of seismic survey activity on the Arctic outer continental shelf — Shell, ConocoPhillips and GX Technologies are all shooting seismic in the Chukchi Sea this summer, while Shell is also shooting seismic in the Beaufort Sea.

The PEA enables MMS to assess the environmental impacts of the surveys as a whole, rather than individually. And, although each individual survey requires its own environmental assessment, that assessment is very straightforward if the survey falls within the scope of the PEA.

A marine seismic survey involves a survey vessel firing an array of air guns in the water at frequent intervals while the vessel traverses a seismic line. The sound emitted from the air guns is reflected from underground rock formations and the ensuing echoes are recorded through an array of geophones that the survey vessel tows behind the air guns. The noise from the guns can disturb or agitate marine wildlife and, in extreme cases, might injure wildlife.

Comprehensive look at impacts

The PEA has taken a comprehensive and detailed look at the potential impacts of seismic surveying on the complete ecosystem of the Beaufort and Chukchi, and on the communities of the region. Of particular concern are the possible impacts on marine mammals such as bowhead whales and seals, and the consequent impacts on the subsistence lifestyle on the Inupiat people who depend on harvesting marine animals for food.

The PEA accepts that any seismic survey work will have at least some impact on wildlife and MMS is still evaluating the consequences of not permitting seismic activities. However, the PEA views a ban of seismic surveys as unacceptable because, if the oil and gas industry does not have the means to effectively evaluate the hydrocarbon resources of the Chukchi and Beaufort seas, “MMS is hampered in its ability to ensure fair market value for leases, make royalty-relief determinations, conserve oil and gas resources and perform other statutory responsibilities.” This “no action” outcome of the PEA would also be inefficient because it would not accommodate cost-effective technologies and would require the use of more limited sources of information, the PEA says.

However, the PEA does require mitigation measures beyond the standard MMS stipulations and guidelines — the existing standards include minimum spacing requirements between seismic vessels, the use of minimum sound levels and the avoidance of groups of whales. MMS rejected the limitation of mitigation measures to these standards as infeasible, because this alternative “does not consider incorporating additional cost-effective protective measures nor does it adequately address social issues related to subsistence-harvest activities.”

Exclusion zones required

MMS now requires mitigation beyond the existing standards through the use of exclusion zones and monitoring zones. The term “exclusion zone” refers to an area around the seismic sound source that must be free of marine mammals. A decibel value specifies the acceptable noise limit within an exclusion zone. A monitoring zone is an area around an observed group of animals — within that zone sound levels must be kept below a specified level.

The acceptable sound levels for exclusion zones and monitoring zones derive from scientific research on the impact of noise on marine mammals. A 120-decibel sound level would protect all marine mammals from behavior harassment. And this level would avoid potential disturbance to bowhead whale cows with calves, as well as to bowhead and gray whale aggregations. A 160-decibel sound level represents the point at which the U.S. National Marine Fisheries Service considers that impulse sounds such as seismic shots start to cause behavior harassment. Sound levels above 180 or 190 decibels could cause hearing damage to various marine mammals, including seals, walruses and whales.

Researchers have reported ambient noise levels in the range 63 to 133 decibels in the Chukchi and Beaufort seas, the PEA says.

The size of an exclusion zone depends on the sound level that the zone protects animals from, because the volume of the air gun shots decays with the distance from the air gun array — a 120-decibel exclusion zone is much larger than a 180/190-decibel exclusion zone. But maintaining a large exclusion zone is less practical and probably more expensive than monitoring a small zone — whereas a small zone might be monitored by marine observers on the seismic vessels, a large zone would likely require continuous aerial animal spotting over a wide area.

MMS has concluded that a 120-decibel exclusion zone is impractical to implement. Although it appears attractive in that it would provide the highest level of protection to marine mammals, “logistical complications and engineering limitations make effective monitoring of the 120-db isopleth-exclusion zone … very difficult and overall not feasible to accomplish,” the PEA says.

Instead, MMS is mandating a 180/190-decibel exclusion zone, but with additional mitigation measures. The additional measures include establishing monitoring zones based on observations from aerial monitoring within 24 hours of seismic survey activity. Observed bowhead whale cow/calf pairs will require 120-decibel monitoring zones and observed aggregations of bowhead or gray whales will require 160-decibel monitoring zones. No seismic survey will be allowed within the monitoring zones.

The agency also requires the seismic survey operators to negotiate a conflict avoidance agreement with the Alaska Eskimo Whaling Commission that will “likely include a prohibition on conducting seismic surveys during the bowhead whale hunting season in the Beaufort Sea, describe a dispute resolution process and provide emergency assistance to whalers at sea.” Traditional knowledge and some scientific research indicate that any level of seismic survey activity can disturb or disrupt a whale hunt.

Operators also have to obtain an incidental-take authorization from the National Marine Fisheries Service — that authorization will specify the NMFS mitigation requirements. and its sister non-profit websites,,,,,, and are owned by John Donovan. There is also a Wikipedia feature.

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