NEW ORLEANS -- Coast Guard crews raced to protect the Gulf of Mexico coastline Monday as a remote sub tried to shut off an underwater oil well that's gushing 42,000 gallons a day from the site of a wrecked drilling platform.
If crews cannot stop the leak quickly, they might need to drill another well to redirect the oil, a laborious process that could take weeks while oil washes up along a broad stretch of shore, from the white-sand beaches of Florida's Panhandle to the swamps of Louisiana.
The oil is escaping from two leaks in a drilling pipe about 5,000 feet below the surface. The leaks threaten hundreds of miles of coastline in four states, with waters that are home to dolphins, sea birds, and prime fishing and tourism areas.
The oil is not expected to reach the shoreline for at least another three days, officials said. The winds and currents can change rapidly and drastically, so officials were hesitant to give any longer forecasts for where the spill will head.
The oil began gushing out of the sea floor after the rig Deepwater Horizon exploded April 20 and sank two days later about 40 miles off the Mississippi River delta. Eleven of the 126 workers aboard at the time are missing and presumed dead; the rest escaped. The cause of the explosion has not been determined.
As of Monday afternoon, an area 48 miles long and 39 miles wide was covered by oil that leaked from the site of the rig, which was owned by Transocean Ltd. and operated by BP PLC.
Crews used robot submarines to activate valves in hopes of stopping the leaks, but they may not know until today if that strategy will work. BP also mobilized two rigs to drill a relief well if needed. Such a well could help redirect the oil, though it could also take weeks to complete, especially at that depth.
Kenneth E. Arnold, an offshore production facility expert, said relief wells pose serious engineering challenges.
"Sometimes you have to drill through the steel, and that's what happened in Australia," he said, referring to a blowout last August on a rig called the West Atlas in the Timor Sea. "It took them three times before they were successful."
Not until November could mud be pumped through a relief well to shut off the deepwater spigot. The spill has resulted in major environmental damage along the coast of East Timor and Indonesia.
BP plans to collect leaking oil on the ocean bottom by lowering a large dome to capture the oil and using pipes and hoses to pump it into a vessel on the surface, said Doug Suttles, chief operating officer of BP Exploration and Production. It could take up to a month to get the equipment in place.
"That system has been deployed in shallower water," he said, "but it has never been deployed at 5,000 feet of water, so we have to be careful."
The U.S. spill, moving slowly north and spreading east and west, was about 30 miles from the Chandeleur Islands off the Louisiana coast Tuesday. The Coast Guard said kinks in the pipe were helping stem the flow of oil.
George Crozier, oceanographer and executive director at the Dauphin Island Sea Lab in Alabama, said he was studying wind and ocean currents driving the oil.
He said Pensacola, Fla., is probably the eastern edge of the threatened area, though no one really knows what the effects will be.
"We've never seen anything like this magnitude," he said. "The problems are going to be on the beaches themselves, that's where it will be really visible."
Aaron Viles, director for New Orleans-based Gulf Restoration Network, an environmental group, said he flew over the spill Sunday and saw what was likely a sperm whale in the oil sheen.
"There are going to be significant marine impacts," he said.
Concern Monday focused on the Chandeleur and Breton barrier islands in Louisiana, where thousands of birds are nesting.
"It's already a fragile system. It would be devastating to see anything happen to that system," said Mark Kulp, a University of New Orleans geologist.
Whales have been spotted near the oil spill, though they didn't seem to be in any stress. The spill also threatened oyster beds in Breton Sound on the eastern side of the Mississippi River. Harvesters could only watch and wait.
"That's our main oyster-producing area," said John Tesvich, a fourth-generation oyster farmer with Port Sulphur Fisheries Co. His company has about 4,000 acres of oyster grounds that could be affected if the spill worsens.
"Trying to move crops would be totally speculative," Tesvich said. "You wouldn't know where to move a crop. You might be moving a crop to a place that's even worse."
He said oil and oysters are not a good mix. If the oyster grounds are affected, thousands of fishermen, packers, processors might have to curtail operations.
Worse, he said, it's spawning season, and contamination could affect young oysters. But even if the spill is mostly contained, he said oil residue could get sucked in by the oysters.
"You will have off-flavors that would be a concern," Tesvich said.
If the oil continues oozing north, the white-sand beaches in Mississippi, Alabama and west Florida could be fouled.
In Louisiana, Gov. Bobby Jindal asked the Coast Guard to use containment booms, which float like a string of fat sausage links to hold back oil until it can be skimmed off the surface. Crews were trying to keep oil out of the Pass A Loutre wildlife area, a 115,000-acre preserve that is home to alligators, birds and fish near the mouth of the Mississippi River.
In Mississippi, Gov. Haley Barbour said he has spoken with the Coast Guard mission commander, Rear Adm. Mary Landry but was uncertain what steps his state might take to protect its beaches.
"It's a real difficulty in trying to determine what defenses will be effective," he said.
A fleet of boats and containment equipment was working to skim oil from the surface of the Gulf late last week. But a weather system that spawned deadly tornadoes in Louisiana and Mississippi and stirred up heavy seas over the weekend forced crews to suspend their efforts.
Coast Guard Petty Officer Connie Terrell said 32 vessels are waiting for conditions to improve to resume the cleanup. She could not say when they will be back at work, but she said 23,000 feet of containment boom had been deployed, 70,000 more were ready to go when the effort resumes, and another 50,000 feet were on order.
Associated Press writers Kevin McGill in New Orleans, Emily Wagster Pettus in Yazoo City, Miss., and Melinda Deslatte in Baton Rouge contributed to this story.