By Matthew Bigg
VENICE, Louisiana (Reuters) - BP <:BP.LO:>engineers prepared on Thursday to start lowering a 98-ton metal chamber over a ruptured undersea oil well in the Gulf of Mexico, trying to control a spill that threatens an environmental catastrophe for the U.S. shoreline.
The barge carrying the massive white-painted box arrived at the site of the spill where a BP-owned well blew out two weeks ago 40 miles/64 km off the Louisiana coast, causing the explosion and sinking of the Deepwater Horizon rig.
Oil workers, volunteers and the military have been battling desperately to shut off the gushing oil leak and stop the huge spreading slick from reaching major ports, tourist beaches, wildlife refuges and fishing grounds on the U.S. Gulf Coast.
Once lowered to the seabed, an operation that could take two days, the massive riveted metal containment dome is designed to capture and channel leaking oil to a drilling ship on the surface, and BP said it could begin doing this by Monday.
But company officials, facing enormous pressure to limit the ecological and economic damage from the accident, cautioned the device had never been used in water nearly 1 mile deep.
Prevailing winds kept the giant oil slick offshore two weeks after the Deepwater Horizon drilling rig accident triggered the breach, and it was barely moving.
"If you look at our trajectory for the next 72 hours, they don't show a whole lot of real movement from where it's at," said Charlie Henry, a meteorologist with the National Oceanic and Atmospheric Administration.
The calm weather allowed for a series of "controlled burns" of the massive slick on Wednesday, the first such attempts since a 28-minute blaze on April 28 that removed thousands of gallons of fuel.
Throughout the Gulf Coast, crews deployed miles (kilometers) of protective booms to block the slick and used dispersants to break up the thick oil before it fouls tourist beaches and fishing grounds, threatening an environmental catastrophe.
BP has capped one of three leaks in the ruptured well, but oil is still flowing at an unchanged 5,000 barrels (210,000 gallons/795,000 liters) a day.
It has started drilling a relief well, but that could take two or three months to complete.
INSPECTION TOUR
Homeland Security Secretary Janet Napolitano, Commerce Secretary Gary Locke and other administration officials will travel to Biloxi, Mississippi, on Thursday to review relief operations and meet with officials.
Obama administration officials were reviewing the practice of granting exemptions from environmental impact studies for oil exploration projects deemed to involve little risk. The Minerals Management Service had exempted BP from a detailed environmental review of the project.
U.S. government agencies grant the so-called categorical exclusions for types of projects typically found to not have substantial environmental impacts, or in cases where the agency has past experience with a similar projects.
Driller Transocean Ltd said the U.S. Justice Department asked it to preserve records related to the well's drilling and the deadly blast on its rig two weeks ago.
BP shares rose to nearly 572 pence on Thursday, gaining 1.2 percent, as bargain hunting has emerged after almost two weeks of declines wiped more than $32 billion from the company's market value. The STOXX Europe 600 Oil and Gas index stayed relatively steady.
Authorities are on alert for the first major landfall of the oil slick, estimated to be at least 130 miles by 70 miles in size, and scientists monitored the impact on marine and coastal wildlife in the region.
Anthony Nelson, one of thousands of idled shrimpers, oystermen and fishermen in Bayou La Batre -- the heart of Alabama's seafood industry -- signed up to help BP contain the oil spill.
He spent hundreds of dollars getting his small fleet of nine vessels Coast Guard-certified for cleanup duty while waiting to hear if he would be called into service. Still, he said laying boom in the gulf will earn a fraction of what shrimping would pay.
"We'll help them clean it up, but we rather go to work," Nelson said. "I'm 55, and by the time they open this back up again (for fishing), I'll be dead, or I'll be in a convalescent home."
(Additional reporting by Matt Daily in New York and Tom Bergin in London; Anna Driver and Chris Baltimore in Houston; Tom Brown and Pascal Fletcher in Miami; Michael Peltier in Pensacola; Brian Snyder in Mobile, and Richard Cowan in Washington; Writing by John Whitesides; Editing by Vicki Allen)
