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Estimates of oil leak gush past twice the previous levels; drill permits yanked

The Deepwater Horizon oil spill has surpassed the size of the 1969 Santa Barbara spill and the Exxon Valdez. Here are some other historical spills.

Even if the well is plugged this weekend, the spill already is of epic proportions. The Flow Rate Technical Group, a task force made up of scientists from government and academia, has produced preliminary estimates that 12,000 to 19,000 barrels a day have leaked into the gulf, U.S. Geological Survey Director Marcia McNutt said Thursday.

The scale of the spill has been a matter of furious debate and speculation. The Coast Guard initially pegged the spill at 1,000 barrels a day. Then the National Oceanographic and Atmospheric Administration used satellite images to make an estimate of 5,000 barrels a day.

Government officials and BP executives repeated that figure for weeks, even as independent scientists came up with figures as high as 95,000 barrels a day.

There are 42 gallons in a barrel. Assuming that the leak began when the Deepwater Horizon drilling rig sank to the gulf bottom on April 22, and subtracting the amount of oil that BP said it has siphoned from the leaking pipe and pumped onto a barge, the new estimate would suggest that 17 million to 27 million gallons of oil have polluted the gulf.

The 1989 Exxon Valdez spill, by comparison, put 11 million gallons of oil along more than 1,000 miles of Alaska's coastline.

Interior Department spokesman Frank Quimby said scientists used multiple techniques. One took video of the plume of oil escaping from the pipe and fed it through computer models. The result was 12,000 to 25,000 barrels a day.

Another technique relied on a NASA plane that could differentiate oil from water on the gulf surface. That produced an estimate of 12,000 to 19,000 barrels a day. A third method relied on measurements from the insertion tube that siphoned oil from the end of the riser. That produced an estimate of 12,000 barrels a day.

Also Thursday, scientists from the University of South Florida reported the discovery in the gulf of a "plume" of dissolved oil that was six miles wide and up to 20 miles long. The plume extended from the surface down to a depth of 3,200 feet.

The oil is entirely dissolved in the water, which appears clear, USF professor David Hollander said. That seemed to confirm the fears of some scientists that, because of the depth of the leak and the heavy use of chemical dispersants, this spill was behaving differently than others. Instead of floating on top of the water, it may be moving beneath it.

That could hamper containment efforts and would also be a problem for ecosystems deep under the gulf. There, scientists say, the oil could be absorbed by tiny animals and enter a food chain that builds to sportfish such as red snapper. It might also glom on to deep coral formations.

Oil has now hit 101 miles of Louisiana coastline, state officials said, mainly lapping up on state's outer ring of uninhabited barrier islands: Whiskey Island, Raccoon Island, Isle Grand Terre. The beaches and marinas of Grand Isle -- a rare beach in a region of marshy coast, and a weekend destination for Cajuns and deepwater fishermen -- are deserted, except for those working on the spill.

"We should have about 4,500, 5,000 people on the beach," said Mayor Dave Camardelle at a news conference with Gov. Bobby Jindal (R) Thursday. "And it's a ghost town."

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