ON THE GULF OF MEXICO - BP lowered a 100-ton concrete-and-steel vault onto a ruptured well in the Gulf of Mexico on Friday, an important step in a delicate and unprecedented attempt to stop most of the gushing crude fouling the sea.
Underwater robots guided the 40-foot-tall box into place. Now that the contraption is on the seafloor, workers will need at least 12 hours to let it settle and make sure it's stable before the robots can hook up a pipe and hose that will funnel the oil up to a tanker.
"It appears to be going exactly as we hoped," BP spokesman Bill Salvin told The Associated Press on Friday afternoon, shortly after the four-story device hit the seafloor. "Still lots of challenges ahead, but this is very good progress."
By Sunday, the box the size of a house could be capturing up to 85 percent of the oil. So far about 3 million gallons have leaked in an environmental crisis that has been unfolding since a deepwater drilling platform exploded April 20, sending toxic oil toward a shoreline of marshes, shipping channels, fishing grounds and beaches. Eleven workers were killed in the accident.
The lowering of the containment device was a slow-moving drama playing out 50 miles from Louisiana's coast, requiring great precision and attention to detail. It took about two weeks to build the box, and the effort to lower it by crane and cable to the seafloor began late Thursday night. After it hit bottom Friday afternoon, the crane gradually eased off to allow it to settle.
"We are essentially taking a four-story building and lowering it 5,000 feet and setting it on the head of a pin," Salvin said.
Also Friday, rig workers told BP's internal investigators that the oil well's deadly blowout was triggered by a methane gas bubble that escaped and shot toward the surface.
The interviews were described in detail to an AP reporter by an oil pipeline safety expert who received them from former industry colleagues seeking his opinion.
Deep beneath the seafloor, methane gas is in a slushy, crystalline form. As the workers removed pressure from the well and introduced heat, the cement seal around the pipe destabilized, creating a gas bubble. It intensified and grew, breaking through the rig's various safety barriers.