NOAA reports underwater cloud of diffuse oil

Paula Dittrick
OGJ Senior Staff Writer

HOUSTON, June 24 -- The National Oceanic and Atmospheric Administration said scientific researchers have found no conclusive evidence that underwater oil exists more than 6 miles from the Macondo wellhead.

On June 23, NOAA released a peer-reviewed, analytical summary report from the Joint Analysis Group (JAG) regarding subsea monitoring. The report contradicts earlier suggestions by some that massive oil plumes exist in the Gulf of Mexico subsea.

NOAA described a “cloud of diffuse oil” in 3,300-4,600 ft of water near the wellhead, which is in 5,000 ft of water on Mississippi Canyon Block 252.

Preliminary findings indicated total petroleum hydrocarbon concentrations at 3,300-4,600 ft in concentrations of 1-2 ppm, which is small enough to be below “immediate levels of concern,” NOAA said in a news release.

“Analysis also shows that this cloud is most concentrated near the source of the leak and decreases with distance from the wellhead,” NOAA said. “Beyond 6 miles from the wellhead, concentration of this cloud drop to levels that are not detectable.”

Monitoring data of the subsea has been used on an ongoing basis to help guide decisions by federal officials regarding the continued use of subsea dispersant, which continues to be used (OGJ, May 24, 2010, p. 22).

Some 1.47 million gal of total dispersant have been applied—972,000 gal on the surface and 493,000 gal at the wellhead—federal officials reported June 24.

Chemical dispersants break up the oil, enabling it to degrade faster. The US Environmental Protection Agency and NOAA monitored dispersants applied at the subsea level and took water samples to understand its affects upon the marine environment and aquatic life.

“The report concludes that decreased oil droplet size in deep waters is consistent with chemically dispersed oil,” NOAA said. “The report also shows that dissolved oxygen levels remain above immediate levels of concern, although there is a need to monitor dissolved oxygen levels over time.”

Dispersants are part of the spill response strategy to prevent more oil from reaching wetlands, marshes, and beaches by breaking up the oil and speeding its natural degradation offshore.

“The JAG will continue to analyze subsea data and make its reports available to the public as quickly as possible to ensure Americans have access to the data government agencies are using to make decisions,” NOAA said.

Contact Paula Dittrick at paulad@ogjonline.com.



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