The oil giant BP has permanently sealed the ruptured Gulf of Mexico well that led to the worst oil spill in US history. On Sunday, the Coast Guard announced the completion of a relief well that will prevent any chance of a future spill. The well has been sealed since mid-July but could not be declared “dead” until the relief well was installed. Eleven workers were killed in the April 20th blast that tore open the well. Some 206 million gallons of oil spewed into the Gulf.