If current estimates for the Deepwater Horizon oil leak in the Gulf of Mexico are correct, the massive spill could eventually dwarf that of Exxon Valdez spill of 1989 — previously the largest in U.S. history — by as much as three times. At a rate of 5,000 barrels a day, for an estimated 90 days, well over 20 million gallons of crude could be pumped out onto the Louisiana coastline.