Crews working on a ruptured oil well deep beneath the Gulf of Mexico planned Sunday to begin offloading equipment for a new attempt to seal the flow of crude gushing into the sea.
The equipment being offloaded from one of the vessels anchored above the leaking well, about 1.6 kilometres beneath the surface, would block the oil flow by shooting mud and concrete directly into the well's blowout preventer.
That process could take two to three weeks.
In the meantime, crews have moved a giant oil containment box -- earlier used in an attempt to stop the flow of oil -- off the site of the leak and parked it on the seabed nearly 500 metres away.
The containment box was successfully lowered over the massive oil leak Saturday, but had to be lifted off when ice-like crystals formed inside it and blocked the flow of oil out of the top of the box.
The 100-ton steel and concrete box was moved hundreds of feet away while officials tried to figure out their next move.
"I wouldn't say it's failed yet," BP chief operating officer Doug Suttles said of the containment box. "What I would say is what we attempted to do ... didn't work."
It had taken nearly two weeks to build the box, cart it 80 kilometres out to the leak site and slowly lower it to the bottom.
BP officials were not giving up hope that a containment box -- either the one already on the seabed or another one under construction nearby -- could cover the well. But they said it could be Monday or later before they decide whether to make another attempt to use the box to capture the oil and funnel it to a tanker at the surface.
Suttles said the company is looking into options such as raising the massive containment box high enough that warmer water would prevent the ice-like slush from forming, or using heated water or methanol to melt the crystals.
Suttles said BP may also try putting a smaller containment dome over the massive leak, believing that it would be less vulnerable to ice-like crystals. The smaller dome could be ready to deploy Tuesday or Wednesday.
The company is also now debating whether it should cut the riser pipe undersea and use larger piping to bring the gushing oil to a drill ship on the surface. Cutting the pipe would be tough, and was considered the less desirable option, said Suttles.
As BP weighed its options on the mainland, waves of dark brown and black sludge crashed into vessels in the area above the leak. The fumes there were so intense that crewmembers of the support ship Joe Griffin had to wear respirators while on deck.
Even as officials pondered their next move, Coast Guard Rear Adm. Mary Landry said she must continue to manage expectations of what the containment box can do.
"This dome is no silver bullet to stop the leak," she said.
But the captain of the supply boat that carried the hulking, four-storey-tall vault for 11 hours from the Louisiana coast last week wasn't giving up hope.
"Everybody knew this was a possibility well before we brought the dome out," said Capt. Demi Shaffer, of Seward, Alaska. "It's an everyday occurrence when you're drilling, with the pipeline trying to freeze up."
BP spokesman Mark Proegler said that no decisions have been made on what step the company will take next.
Three options are being considered, Proegler said, including the technique known as a "top kill" to shoot mud and concrete into the well and create a plug to stop the crude oil gushing into the sea.
BP is also drilling sideways into the blown-out well in hopes of plugging it from the bottom, a process that could take two to three months.
While the company's crews try to figure out their next move, the leaking well is spilling 757,000 litres of crude oil into the Gulf each day.
Early Sunday, there was little visible new activity at the site of the spill. The skies were clear, but wind and waves were picking up.
Thick blobs of tar have begun washing up on Alabama's white sand beaches, in another sign the spill is spreading.
The balls of tar, some the size of golf balls, washed up Saturday on Dauphin Island, five kilometres off the Alabama mainland at the mouth of Mobile Bay and much farther east than the thin, rainbow sheens of oil that have so far been seen only sporadically in the Louisiana marshes.
In the nearly three weeks since the Deepwater Horizon rig exploded April 20, killing 11 workers, about 13.25 million litres of crude has poured into the sea, or about a third of the amount spilled in the Exxon Valdez disaster.
Officials say more than 300 kilometres of booms have been put out to try to contain the oil.
The Coast Guard and other officials cleaning up the mess said Sunday that about 3.4 million gallons of an oil-water mix has been collected and crews have used nearly 309,000 gallons of chemicals to break up the oil on the water's surface.
The spot where the Deepwater Horizon rig exploded and sank now teems with vessels working on containing the rogue well. There are 15 boats and large ships at or near the site -- some being used in an ongoing effort to drill a relief well, considered a permanent if weeks-away fix.
With files from The Associated Press
