By Bettina Boxall and Louis Sahagun, Los Angeles Times
Crews were expected to spend much of the weekend assembling a mile-long pipe system leading to an underwater containment dome that by Monday could start catching the oil spilling into the Gulf of Mexico in a swirl of contamination.
The metal containment device, which resembles a 4-story, boxy version of the "Wizard of Oz" Tin Man, was being lowered gently Friday into position over the main leak feeding the Deepwater Horizon oil spill.

Placing the dome is the first step in a laborious process that could easily go awry. "This is going to take a few days … and it may or may not work," said Coast Guard Rear Adm. Mary Landry.
If it does work, the dome won't shut down the fountain of crude spurting from a broken pipe on the muddy gulf floor. "This is not the final solution," Landry said. But it could capture most of the oil and funnel it 5,000 feet upward to a waiting ship.
While BP moves ahead with the containment strategy, the company is also plotting how to plug the blown-out wellhead that has spewed an estimated 3 million gallons of oil since a deadly April 20 explosion on the Deepwater Horizon offshore rig.
"We're going to continue to look for every option we can find," BP Chief Operating Officer Doug Suttles said.
The company has flown in 20 experts from around the world and is even reviewing suggestions from a public call-in line.
Suttles said BP has discarded some ideas for stopping the oil gusher and is now evaluating two other options. One would involve installing a new blowout preventer device over the one that failed.
The other strategy would be as simple as stuffing the broken preventer with rubber cuttings, rather like stopping up a toilet.
A company spokesman declined to comment Friday night on an Associated Press report that said rig workers have told BP investigators that the blowout was triggered by a bubble of methane gas that escaped from the well and shot up the drill column.
According to the AP, company interviews with the rig crew indicate that as workers released pressure from the drilling column and introduced heat to set the cement seal around the wellhead, a chemical reaction created a gas bubble and the cement around the pipe destabilized.
Industry experts have said that natural gas mixed with oil may have leaked up the long drilling pipe, expanding as it rose and then exploding with a spark at the surface.
Good weather in recent days has allowed cleanup teams to continue to skim and burn oil on the water's surface. "We are very thankful for the weather," Landry said. Crews have conducted at least four separate burns, sending billowing black clouds of smoke toward the gulf sky and consuming more than 7,000 barrels of oil. Planes dropped more dispersants to break up floating oil.
With the amoeba-like oil slick hovering just off the Louisiana coast and washing up on some barrier islands, Louisiana politicians have complained that not enough booms have been laid to protect their shores. BP officials said more than 150 miles of booms have been deployed where oil is most likely to wash ashore.
"Everyone would like to be able to boom everything. That's not possible," Suttles said.
In other developments, a spokesman for the U.S. Minerals Management Service said 30 deep-water rigs in the gulf have been inspected since the Horizon explosion and the agency has found no cause for concern.
The National Oceanic and Atmospheric Administration enlarged the boundaries of its no-fishing zone in federal waters to reflect the growing spill and extended the restrictions to May 17. But the agency said the vast majority of gulf waters remain unaffected by the disaster.
The slick, at times eerily beautiful as it creeps across the gulf in a shifting pattern of mustard and rust, moved west Friday and continued to threaten the shores of the Mississippi Delta, Breton Sound and Chandeleur Sound, according to NOAA.
Three teams were sent to inspect the Chandeleur Islands, where a sheen of oil has washed up, potentially contaminating parts of the second-oldest wildlife refuge in the national system.
"It's breaking my heart, and the smell of this water is making me nauseous," said Linda St. Martin, a Sierra Club policy consultant, as she bobbed in a boat near the barrier chain, a nesting spot for thousands of brown pelicans.
Oil first made landfall on the crescent-shaped chain Wednesday. By Friday morning, the effects were evident in lapping oil and a distinct lack of birds, said Capt. Mark Stebly, a fishing guide who has lived on one of the islands for 25 years.
The refuge is a breeding ground for thousands of birds, including brown pelicans. Hundreds of frigate birds — large dark seabirds with the longest wingspan, in proportion to their weight, of all birds — roost in the mangroves .
"It's a terrible, disgusting reddish-brown scum floating around my boat," Stebly said in a telephone interview. "It's gathering in the shallows where horseshoe crabs are breeding."
"Almost all the birds got the hell out of there; the only birds left on the island have nests," he said. "It's like a damn Twilight Zone scene."