The barge Joe Griffin sails down a channel on its way to the Gulf of Mexico carrying the 100-ton concrete-and-steel containment chamber that will be used to help contain oil leaking from a blown-out wellhead.
BP engineers started late Thursday lowering a giant concrete cap over a blown-out wellhead on the bottom of the Gulf of Mexico — a desperate move to contain the leak spewing an estimated 200,000 gallons of crude oil a day into the surrounding waters.
The barge Joe Griffin arrived at the source of the leak carrying the 100-ton concrete-and-steel contraption known as a "cofferdam" Thursday morning. But the lowering of the box was delayed because of dangerous fumes rising from the oily water in the windless night, the captain of the supply boat hauling the box told The Associated Press. A spark caused by the scrape of metal on metal could cause a fire, Capt. Demi Shaffer said.
If it works, the system could collect as much as 85 percent of the oil that's been leaking nearly a mile down, and direct it to the surface so it can be contained and removed.
The mission took on added urgency as oil started washing up on delicate barrier islands.
A sheen of thick, tar-like oil surrounded the vessel at the site 50 miles off the Louisiana coast. Engineers say the cap is the best short-term solution for controlling the gusher since the Deepwater Horizon offshore drilling rig exploded and sank two weeks ago, killing 11 people.
The Joe Griffin was expected to meet up with a Norwegian vessel, the Boa Sub C, equipped with a crane that will be used to lower the cap to the wellhead.
BP spokesman Bill Salvin said the drop is expected at about noon local time Thursday.
Such an operation has never been tried at such extreme depth, said Doug Suttles, the British oil giant's chief operating officer.
"You can imagine we're landing a very, very large metal building on the sea floor to capture the flow," he said. "This has to be done at a depth of 5,000 feet, so it's a complex task."
Once the cap nears the seabed, remotely operated underwater vehicles will be used to guide it into place. A steel pipe will be attached to a tanker at the surface and connected to the top of the cap to move the oil.
A boat uses a boom and absorbent material to soak up oil in Cat Bay, near Grand Isle, La., on June 28. A tropical storm is expected to hit the Gulf and impede cleanup efforts.
Joe Raedle/Getty Images
Florida Gov. Charlie Crist and wife Carole Rome Crist (right) stand with others during a Hands Across the Sand event June 26 in Pensacola, Fla. The event was staged across the nation to protest offshore oil drilling.
Joe Raedle/Getty Images
Oil clouds the surface of Barataria Bay near Port Sulpher, La., on June 19.
Sean Gardner/Getty Images
Workers adjust piping while drilling a relief well at the site of the Deepwater Horizon oil spill.
Charlie Neibergall/Getty Images
A dolphin rises up out of the water near Grand Terre Island off the coast of Louisiana on June 14.
Derick E. Hingle/AP
President Obama stands with Mississippi Gov. Haley Barbour (right) and Gulfport, Miss., Mayor George Schloegel after meeting with residents affected by the oil spill.
Crude oil washes ashore in Orange Beach, Ala., on June 12. Oil slicks, 4 to 6 inches thick in some parts, have washed up along the Alabama coast.
A volunteer uses a toothbrush to clean an oil-covered white pelican at the Fort Jackson Oiled Wildlife Rehabilitation Center in Buras, La., June 9.
Saul Loeb/AFP/Getty Images
A shrimp boat skims oil from the surface of the water just off Orange Beach, Ala., as a family enjoys the surf. Oily tar balls have started washing up on Orange Beach and beaches in the western Florida panhandle.
Sand from a dredge is pumped onto East Grand Terre Island, La., to provide a barrier against the Deepwater Horizon oil spill, June 8.
A dead turtle floats on a pool of oil from the Deepwater Horizon spill in Barataria Bay off the coast of Louisiana on June 7.
Workers use absorbent pads to remove oil that has washed ashore from the spill in Grand Isle, La., June 6.
Plaquemines Parish coastal zone director P.J. Hahn lifts an oil-covered pelican out of the water on Queen Bess Island in Plaquemines Parish, La., June 5.
Heavy oil pools along the side of a boom just outside Cat Island in Grand Isle, La., June 6.
Win McNamee/Getty Images
President Obama walks alongside Grand Isle Mayor David Camardelle (from right), U.S. Coast Guard Adm. Thad Allen, who is in charge of the federal response to the spill, and Chris Camardelle after meeting with local business owners in Grand Isle, La., June 4.
Saul Loeb/AFP/Getty Images
A brown pelican sits on the beach at East Grand Terre Island along the Louisiana coast after being drenched in oil from the BP Deepwater Horizon oil spill, June 3.
U.S. Attorney General Eric Holder announces that the Justice Department has launched a criminal investigation into the BP oil spill. With him, from left: Stephanie Finley and Jim Letten, U.S. attorneys for the Western District of Louisiana; Ignacia Moreno, assistant attorney general for the Environment and Natural Resources Division; Tony West, assistant attorney general, Civil Division; and Don Burkhalter, U.S. attorney for the Southern District of Mississippi.
The oil slick off the coast of Louisiana, seen from above.
NASA via Getty Images
A worker leaves the beach in Grand Isle, La., on May 30. BP is turning to yet another mix of undersea robot maneuvers to help keep more crude oil from flowing into the Gulf.
Jae C. Hong/AP
Protesters cover themselves with a water and paint mixture during a demonstration at a BP gas station in New York City on May 28.
Workers clean up oil in Pass a Loutre, La. The latest attempt to plug the leak was unsuccessful.
Jae C. Hong, File/AP
Residents listen to a discussion with parish officials and a BP representative on May 25 in Chalmette, La. Officials now say that it may be impossible to clean the hundreds of miles of coastal wetlands affected by the massive oil spill.
Sean Gardner/Getty Images
An oil-soaked pelican takes flight after Louisiana Fish and Wildlife employees tried to corral it on an island in Barataria Bay on the coast of Louisiana. The island, which is home to hundreds of brown pelican nests as well at terns, gulls and roseate spoonbills, is impacted by oil from the Deepwater Horizon spill.
A sign warns the public to stay away from the beach on Grand Isle, La. Officials closed the oil-covered beaches to the public indefinitely on Saturday.
John Moore/Getty Images
Pelican eggs stained with oil sit in a nest on an island in Barataria Bay on May 22.
A bird flies over oil that has collected on wetlands on Elmer's Island in Grand Isle, La., May 20. The oil came inland despite oil booms that were placed at the wetlands' mouth on the Gulf of Mexico.
Members of the Louisiana National Guard build a land bridge at the mouth of wetlands on Elmer's Island.
The hands of boat captain Preston Morris are covered in oil after collecting surface samples from the marsh of Pass a Loutre, La., on May 19.
Louisiana Gov. Bobby Jindal (center) and Plaquemines Parish President Billy Nungesser (right) tour the oil-impacted marsh of Pass a Loutre, La. "This is the heavy oil that everyone's been fearing that is here now," said Jindal.
BP Chairman and President Lamar McKay (left), with Transocean President and CEO Steven Newman (center) and Applied Science Associates Principal Deborah French McCay, testifies during a Senate Committee on Commerce, Science, and Transportation hearing May 18 on response efforts to the Gulf Coast oil spill.
Manuel Balce Ceneta/AP
This undated frame grab image received from BP and provided by the Senate Environment and Public Works Committee shows details of the oil spill in the Gulf of Mexico. BP has agreed to display a live video feed of the oil gusher on the Select Committee on Energy Independence and Global Warming Committee's website beginning Thursday evening.
Senate Environment and Public Works Committee/AP
President Obama speaks with local fishermen about how they are affected by the oil spill in Venice, La., on May 2.
Saul Loeb/AFP/Getty Images
Danene Birtell with Tri-State Bird Rescue and Research tends to a Northern Gannet in Fort Jackson, La., on April 30. The bird, normally white when full grown, is covered in oil from the oil spill.
Since the explosion, a third oil leak has been discovered in the blown-out well.
In this aerial photo taken April 21 more than 50 miles southeast of Venice, La., the Deepwater Horizon oil rig burns.
Tendrils of oil mar the waters of the Gulf of Mexico in this satellite image taken Monday. An estimated 5,000 barrels of oil a day are seeping into the Gulf, after an explosion last week on a drilling rig about 50 miles off the Louisiana coast.
Courtesy of Digital Globe
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"It's very dark down there ... and we will have lights on the [submersibles], and we know exactly where to put this and guide it into place," said David Clarkson, BP's vice president for project execution.
But even if crews are able to successfully lower the structure in place over the leaking pipeline, there are other potential problems. At 5,000 feet, the water is just 10 degrees above freezing. That, combined with crushing pressure at that depth, could cause the siphon pipe to clog up and prevent the oil from being channeled to the surface. To combat that problem, crews plan to continuously pump warm water and methanol down the pipe to dissolve any clogging.
Engineers also worried about the volatile cocktail of oil, gas and water when it arrives on the ship above, but they believe the liquids can be safely separated without an explosion.
Meanwhile, Interior Secretary Ken Salazar halted all new offshore drilling permits nationwide until at least the end of the
month while the government investigates the Gulf spill.
On Wednesday, BP announced the first small success in containing the spill. Using robotic submarines, the company's engineers managed to install a valve on the leaking pipes — sealing off one of three holes. It won't reduce the amount of oil being discharged but does set the stage for further attempts to stem the flow, company officials said.
Meanwhile, a rapid response team planned to head to the Chandeleur Islands off Louisiana on Thursday to look into unconfirmed reports that oil from the spill had made landfall there, Coast Guard Petty Officer Erik Swanson said.
Dozens of boats have been working around the clock in recent days, laying and repositioning inflatable booms designed to halt the surface flow of the oil slick, which threatens beaches, fragile marshes and wildlife along the U.S. Gulf Coast.
Globules of oil are already falling to the bottom of the sea, endangering virtually every link in the ocean food chain.
Scientists say bacteria, plankton and other tiny, bottom-feeding creatures that might consume the oil will be eaten by small fish, crabs and shrimp. They, in turn, will be eaten by bigger fish, such as red snapper, and marine mammals like dolphins.
There was also concern that the slick could get into the powerful north-flowing Gulfstream current and move up the East Coast.