The Bureau of Ocean Energy Management is allowing offshore energy exploration to take place along the East Coast, using controversial seismic air guns to find gas and oil deposits. A feature about the surveys and the safeguards in place to mitigate impacts to marine life.
It’s a controversial move… but now, most of the eastern seaboard is open to offshore energy exploration. Today, we talk to experts about what that may entail. Just last week, the Bureau of Ocean Energy Management issued a record of decision that allows geological and geophysical survey activities for the purpose of updating data on offshore resources. Acting Director for the Bureau of Ocean Energy Management Walter Cruickshank says the surveys will update information that’s four decades old.
"There were seismic surveys that were taken back in the 1970’s and early 1980’s. That was using older technology that couldn’t see as far underneath the seabed as current technology.”
The Bureau of Ocean Energy Management approved a variety of methods for conducting the surveys, including electromagnetic, gravity, and remote sensing surveys. One of the more controversial methods uses seismic air cannons that shoot a pulse into the water in search of oil and gas deposits deep in the ocean floor.
“Those are conducted by using compressed air guns if you will that are towed behind ships. These are cylinders filled with compressed air and when that air is released, they create a sound wave. And the sound wave will penetrate the seabed and reflect off the layers of rock beneath the seabed. The seismic vessels are towing hydrophones that will listen for those reflected sound waves and use the data from those sound waves to map the subsurface.”
The blasts of air in the water – comparable to the volume of dynamite – will occur every 10 to 15 seconds and can continue for months at a time. Some worry using high volume air guns could impact marine mammals and fish who rely on their sense of hearing in order to survive. Associate Professor of Animal Medicine at North Carolina State University Dr. Craig Harms.
“High energy noise has also been associated with strandings of particularly deep diving dolphins and whales like beaked whales probably because of a behavioral effect that it modifies their surfacing and diving intervals and they develop gases in their blood, so they can develop a “bends” like condition.”
Harms says hearing loss can also occur in dolphins and whales in the vicinity of seismic surveys. The explosions of air generate sound pressure levels in excess of 180 decibels. To put that into perspective, a jet engine registers under that at 140 decibels.
Humpback whales and the endangered right whale depend on echolocation to communicate and navigate their environment. The low frequency of the seismic pulses, which are in the 100 to 200 Hz range, is in the same frequency range that the whales use. In addition to whales and dolphins, certain fish species and sea turtles may also be impacted by the seismic air gun surveys.
“I’ve done some work over at the Duke Lab, Wendy Piniak who’s a graduate student there, did a lot of hearing studies on sea turtles. Don’t really know what effect those noises will have on their behaviors but we know that it’s going to be active in the range that they hear.”
Despite possible impacts to a variety of ocean creatures, offshore energy exploration holds possibility for oil and gas resources that could translate into jobs and revenue for the state. In order to reduce or eliminate impacts to marine life, the Bureau of Ocean Energy Management issued their Record of Decision that implements the “strongest practicable safeguards” to protect humans, marine animals, and coastal environments while moving forward with the geological and geophysical surveys. Acting Director of BOEM Walter Cruickshank thinks the exclusion zone around the vessel will act to protect marine life from survey activity.
“That zone is designed to make sure that no marine mammals can come within at least 500 meters, it could be farther depending on the sound levels. But it’s designed to make sure that the animals will not be exposed to a sound level that could cause injury.”
Visual monitoring by trained protected species observers will be required before and after seismic surveys. If an animal is spotted, seismic air gun activities will be shut down. Associate Professor of Animal Medicine at North Carolina State University Dr. Craig Harms says that problem is when observers only see animals from the surface.
“Some of the whales and dolphins that are particularly affected by sound acoustic events in the past are the beaked whales, which spend so much time at depth and very little time on the surface that you just might not see them.”
Associate Professsor at the Duke Marine Lab Doug Nowacek agrees.
“The boats are required to have marine mammal observers but this does no good in rain, or fog, or at night, or what have you.”
Nowacek studies how sound travels through the water and how marine animals use sound to communicate and explore their environment. He says the 500 meter exclusion area is not enough because low frequency explosions travel through the water with relative ease.
“There was a report a couple of years ago documenting seismic signals being recorded on the mid-Atlantic ridge. So, half way across the Atlantic Ocean, from surveys that were taking place off Nova Scotia and Brazil some 4,000 km from the source, those signals are still detectable.”
Studies show that exposure to sound pressure levels of 160 decibels can cause animals to be behaviorally disturbed. When those level rises in excess of 180 decibels, there’s a potential for injury. According to Nowacek, sound pressure levels from the air guns could still be 180 decibels even from 1,500 meters away. That’s three times the distance the Bureau of Ocean Energy Management has set as a minimum requirement for the acoustic exclusion zone. Furthermore, Nowacek says it doesn’t take extreme sound levels to cause damage, just prolonged exposure.
“One of the things we worry about is the actual physiological stress of being in a noisy environment all the time. And we have some signs that marine mammals in particular do experience stress responses in stressful environments.”
In order to mitigate the impacts to marine mammals, such as whales and dolphins, the Bureau of Ocean Energy Management outlines in their Record of Decision that passive acoustic monitoring is required during air gun surveys. This is done by placing stationary or towed hydrophones in the water to listen for vocalizations. Also, a 40 kilometer separation distance is required between vessels simultaneously conducting seismic surveys. The Bureau of Ocean Energy Management is also prohibiting geological and geophysical surveys during certain times of the year to protect the endangered right whale migration patterns. Acting Director of BOEM’s Walter Cruickshank says the Record of Decision doesn’t authorize survey activities, rather, it establishes a framework for how permit applications will be considered.
“In addition to our review of these surveys, the National Marine Fisheries Service will also be conducting a review under the marine mammal protection act. And under that act, the NMFS cannot provide authorization to those surveys unless they can determine in advance that those surveys will not adversely affect any marine mammal species.”
Since offshore energy exploration is allowed along the eastern seaboard, companies can now apply for permits to conduct survey activities from the inner edge of Federal waters to 403 miles offshore. Cruickshank says the permit review process can be lengthy so he doesn’t expect seismic testing to begin until at least Spring of 2015.
Getting oil and gas from offshore sites may not be far off. But Associate Professor of Animal Medicine at NC State Dr. Craig Harms says it’s not too early to start thinking about oil spill containment.
“We have to be sure that we have structures in place to contain or respond to any potential spill. It might seem now that that’s way in the distance and we don’t need to worry about that yet, but really need to start putting mechanisms in place now to deal with that.”
Duke Marine Lab’s Doug Nowacek is mostly concerned with the long term ramifications of conducting seismic surveys and the effects it will have on marine animals.
“There may be two or three or more surveys done over those areas by different companies or even the same company paid for by a different oil company. And these repeat surveys mean you could have the same block of water shot by seismic multiple times so that different companies, essentially get the same data. And what’s more, if we do get downstream to the development of oil fields, those areas are going to be re-shot with seismic every number of years, two three four five years as they monitor the production of those wells.”
Nowack and Harms may have valid concerns. According to reports from the National Resources Defense Council, air gun surveys have dramatically depressed catch rates of commercial fish species across thousands of square miles of ocean, leaving fisherman in Norway and other parts of the world to seek compensation for their losses.
To read BOEM's Record of Decision, click here: http://www.boem.gov/Record-of-Decision-Atlantic-G-G/