1: ( CNN ) On April 20 , 2010 , a final cement seal of an oil well in the Gulf of Mexico failed , causing what has been called the worst environmental disaster in U.S . history and taking the lives of 11 rig workers . 2: The federal government estimated 4.2 million barrels of oil spilled into the Gulf , but BP argued in court that it was much lower . 3: April 20 marks 5 years since the BP oil spill .
1: the worst environmental disaster in U.S . history 2: 4.2 million barrels of oil spilled into the Gulf 3: the BP oil spill