Douglas Peake, the first mate of the supply boat that brought the box to the site, confirmed he received a radio transmission from the nearby vessel lowering the device that said the device would be in position over the well soon.
The transmission said undersea robots were placing buoys around the main oil leak to act as markers to help line up the 40-foot box.
The box was about 4,000 feet underwater before dawn Friday, with another 1,000 feet to go, Coast Guard Petty Officer Shawn Eggert said.
Meanwhile, a separate mission was close to getting under way to spray water around the rig that’s drilling a relief well to try to reduce the level of fumes from the thick oil hampering the crew’s ability to do its work on deck.
A crane late Thursday lowered the containment vessel designed to collect as much as 85 percent of the oil spewing into the Gulf and funnel it up to a tanker. Eventually the crane would give way to underwater robots that will secure the contraption over the main leak at the bottom, a journey that would take hours.
A steel pipe will be installed between the top of the box and tanker. If all goes well, the whole structure could be operating by Sunday.
"We haven’t done this before," said BP spokesman David Nicholas. "It’s very complex and we can’t guarantee it."
Oil giant BP PLC is in charge of cleaning up the mess. It was leasing the drilling rig Deepwater Horizon that exploded 50 miles out in the Gulf of Mexico, killing 11 workers on April 20 and blowing open the well. It has been spewing an estimated 200,000 gallons a day in the nation’s biggest oil spill since the Exxon Valdez disaster in Alaska in 1989.
The quest took on added urgency as oil reached several barrier islands off the Louisiana coast, many of them fragile animal habitats. Several birds were spotted diving into the oily, pinkish-brown water, and dead jellyfish washed up on the uninhabited islands.
"It’s all over the place. We hope to get it cleaned up before it moves up the west side of the river," said Dustin Chauvin, a 20-year-old shrimp boat captain from Terrebonne Parish, La. "That’s our whole fishing ground. That’s our livelihood."
The crew of the semi-submersible drilling vessel Helix Q4000 waited hours longer that expected to hoist the contraption from the deck of the Joe Griffin supply boat because dangerous fumes rising from the oily water on a windless night had delayed the work. Joe Griffin Capt. Demi Shaffer told an Associated Press reporter aboard his boat the fear was that a spark caused by the scrape of metal on metal could cause a fire.
But the crane lifted the containment box from the deck and into the Gulf after 10 p.m. CDT, dark oil clinging to its white sides as it entered the water and disappeared below the surface.
The technology has been used a few times in shallow waters, but never at such extreme depths – 5,000 feet down, where the water pressure is enough to crush a submarine.
The box – which looks a lot like a peaked, 40-foot-high outhouse, especially on the inside, with its rough timber framing – must be accurately positioned over the well, or it could damage the leaking pipe and make the problem worse.
BP spokesman Doug Suttles said he is not concerned about that happening. Underwater robots have been clearing pieces of pipe and other debris near where the box will be placed to avoid complications.
"We do not believe it could make things worse," he said.
Other risks include ice clogs in the pipes – a problem that crews will try to prevent by continuously pumping in warm water and methanol – and the danger of explosion when separating the mix of oil, gas and water that is brought to the surface.
"I’m worried about every part, as you can imagine," said David Clarkson, BP vice president of engineering projects.
If the box works, a second one now being built may be used to deal with a second, smaller leak from the sea floor.
"Hopefully, it will work better than they expect," Peake, said.
Interior Secretary Ken Salazar on Thursday halted all new offshore drilling permits nationwide until at least the end of the month while the government investigates the Gulf spill.
Oil slicks stretched for miles off the Louisiana coast, where desperate efforts were under way to skim, corral and set the petroleum ablaze. People in Mississippi, Alabama and Florida watched in despair.
The dropping of the box is just one of many strategies being pursued to stave off a widespread environmental disaster. BP is drilling sideways into the blown-out well in hopes of plugging it from the bottom. Also, oil company engineers are examining whether the leak could be shut off by sealing it from the top instead.
The technique, called a "top kill," would use a tube to shoot mud and concrete directly into the well’s blowout preventer, BP spokesman Bill Salvin said. The process would take two to three weeks, compared with the two to three months needed to drill a relief well.
Just after sunrise Friday, the crew of the Joe Griffin planned to spray clean water from cannons into the oil-filled waters surrounding the rig drilling the relief well. The goal is to divert some of the oil away from the rig because the fumes have been so intense that the crew of the rig has had difficulty working on its deck, which is critical to the effort to drill the well.
"Right now, we are the only boat in the zone equipped to do it," Shaffer said of the water cannons.
The rig drilling the relief well is the Development Driller III, a vessel owned by Transocean, the same company that owned the rig that exploded 17 days ago.
During a visit to Biloxi, Miss., Homeland Security Secretary Janet Napolitano said of the containment vessel: "I hope it works. But we are still proceeding as if it won’t. If it does, of course, that will be a major positive development."
"We are facing an evolving situation," she warned. "The possibility remains that the BP oil spill could turn into an unprecedented environmental disaster. The possibility remains that it will be somewhat less."
Meanwhile, a six-member board composed of representatives of the Coast Guard and the federal Minerals Management Service will begin investigating the accident next week.
And a federal judicial panel in Washington has been asked to consolidate at least 65 potential class-action lawsuits claiming economic damage from the spill. Commercial fishermen, business and resort owners, charter boat captains, even would-be vacationers have sued from Texas to Florida, seeking damages that could reach into the billions.
"It’s just going to kill us. It’s going to destroy us," said Dodie Vegas, who owns a motel and cabins in Grand Isle, La., and has seen 10 guests cancel.