EPA knew, based on previous surface dispersant applications, that they were generally less toxic than crude, they decreased the risks to the shorelines and to organisms on the water’s surface, and they biodegraded over weeks or days instead of years as oil does, she noted. “However, all the potential long-term effects of the dispersant application on aquatic life, and the unprecedented volume applied in this response—almost 1.8 million gal—certainly warranted caution,” she said.
BP initially asked EPA on Apr. 30 to use dispersants in a novel manner—underwater, at the leak’s source, Jackson told the commission. “The goal of this approach was to break up and degrade the oil before it reached the water’s surface and came closer to our shorelines, our estuaries, and our marine nurseries,” she said.
Since this approach had never been tried, Jackson said that EPA asked BP to provide specific scientific data proving that such an application would actually be effective. Once it determined that the process was working, EPA then ordered BP to implement a rigorous monitoring system and track measurable environmental impacts by monitoring dissolved oxygen and toxicity, she said. It conditionally approved BP’s request on May 14 after making clear to the company that EPA reserved the right to withdraw its approval if environmental impacts outweighed benefits of dispersing the oil.
USCG approval of the subsea application was based on conditions resulting from only have the dispersant option on some days, combined with trying to secure the source of the crude oil release, according to Rear Adm. Mary E. Landry from the US Department of Homeland Security agency’s eight district in New Orleans. When we approved the subsea injection, we felt there could be a reduction in the amount of dispersants used,” she told the commission. “In the final weeks of May, trying to secure the source was critical for the workers’ health and mitigating the impacts on the shoreline.”
Landry said she was aware of the obligations imposed on BP by requiring it to ask daily for permission to use the dispersants, but added: “We had an overall goal of reducing the amounts used and accomplished this over time.”
“The good news is that we did not see significant short-term environmental impacts of using dispersants,” Jackson said. “We did not, and continue to not see, diminished levels of dissolved oxygen. This is a good indicator of overall aquatic health and we saw normal levels in testing near the rig site, where subsurface dispersants were applied. We also saw no significant toxic effects on rotifers, which are sensitive organisms that act as the ‘canary in the coal mine’ for water health.”
Water monitoring continues to indicate that dispersants have not been found in waters on or near the shoreline, she continued. Of more than 2,000 samples generated by the National Oceanic and Atmospheric Administration and nearly 1,200 generated by EPA, Jackson said that only two were above the method detection limit but well below health limits. “While these detections were likely caused by problems with the testing devices, they were immediately investigated and the areas re-sampled,” she said. “In both cases, follow-up testing indicated a ‘nondetection’ of dispersant.”
