Federal scientists say about one-quarter of the BP oil that spilled out of its broken well remains.
A new government report says nearly three-quarters of the oil -- more than 152 million gallons -- has either been collected at the well by BP's cap, burned, skimmed, chemically dispersed, naturally deteriorated, evaporated or dissolved.
That leaves about 53.5 million gallons in the gulf. The amount remaining -- or washed up on the shore -- still is more than four times the size of the 1989 Exxon Valdez spill.
Federal officials say about a quarter of the oil evaporated or dissolved in the warm gulf waters, the same way sugar dissolves in water. Another one-sixth naturally dispersed, because of the way it leaked from the well. Another one-sixth was burned, skimmed or dispersed using controversial chemicals.