The Use of Surface and Subsea Dispersants During the BP Deepwater Horizon Oil Spill

This draft Report from the National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling examines the issues raised by the use of dispersants in the Deepwater Horizon spill.

Dispersants change the distribution, not the amount, of oil within a marine environment. They are chemicals typically applied directly to oil on the water surface in order to break the oil into small droplets that can then mix with water below the surface. The dispersed oil is rapidly diluted, mixing both vertically and horizontally in the water column. While this alleviates high concentrations at the surface, it may expose organisms to lower, but more widespread, concentrations of oil.

The use of dispersants in the aftermath of the Macondo deepwater well explosion was controversial for three reasons. First, the total amount of dispersants used was unprecedented: 1.84 million gallons. Second, 771,000 of those gallons were applied at the wellhead, located 5,067 feet below the surface. Little or no prior testing had been done on the effectiveness and potential adverse environmental consequences of subsea dispersant use, let alone at those volumes. Third, the existing federal regulatory system pre-authorized dispersant use in the Gulf of Mexico without any limits or guidelines as to amounts or duration.

Faced with an emergency, the government had to make decisions about high-volume and subsea dispersant use within time frames that denied officials the opportunity to gather necessary information. The resulting uncertainty even fueled unfounded suspicions that BP was using dispersants without authorization from the government in an effort to mask the oil and to limit its ultimate liability.

This paper considers two issues. The first is how well the government handled the dispersant issues it faced in the absence of necessary scientific information and pursuant to a regulatory regime that had failed to anticipate this kind of problem. The second is how, in light of lessons learned from this recent experience, government procedures and existing laws might be improved to allow for sounder decisions regarding the use of dispersants in the future.