BP could be looking at close to $18 billion in additional fines over the nation's worst offshore oil spill after a federal judge ruled Thursday that the company acted with "gross negligence" in the 2010 Gulf of Mexico disaster. U.S. District Judge Carl Barbier concluded that the London-based oil giant showed a "conscious disregard of known risks" during the drilling operation and bears most of the responsibility for the blowout that killed 11 rig workers and spewed millions of gallons of oil over three months.