Respondent operates oil & gas production facilities in the Outer Continental Shelf of the Gulf of Mexico. Respondent is a permittee; subject to regulations of the Clean Water Act and National Pollutant Discharge Elimination System. The TransOcean Deepwater Horizon experienced an unauthorized discharge of 143 barrels of synthetic based mud on August 3, 2003 at a depth of around 4300 feet in Mississippi Canyon 725.