A Rarity in the Gulf- Success: BP Slices Pipe in Preparation for Cap

June 3, 2010— -- BP successfully cut the lower marine riser pipe at 10 a.m., using giant shears 5,000 feet below the surface of the sea, but it was a "more jagged cut" Coast Guard Adm. Thad Allen told reporters, and therefore will be a looser fitting seal.

Now a containment dome with a rubber seal will be lowered over the severed pipe. Allen called the cut a "significant step forward" and said the leak could be largely sealed today.

This morning Allen told "GMA" that he hopes they will begin funneling oil to the surface as early as today, a long as nothing goes wrong.

"They've got the top hat containment device positioned over the top of the well head. And they will be able to lower that down on a lower marine riser package as soon as they make that cut, and that's connected to a ship on the surface," Allen said on " GMA."

While the pipe was successfully cut this morning and BP hopes to start bringing the oil up today, Allen told "GMA" there could still be complications.

"We encounter technical difficulties in doing things on the sea floor at 5,000 feet that have never been attempted before in some cases," Allen said. "So they adapt. They learn and they keep moving on. They've got other devices that are a little larger in case the fit's not right."

BP had a setback Wednesday when the diamond saw made it almost halfway through the 20-inch pipe but then became stuck inside the riser pipe. It took 12 hours to get the blade out. BP abandoned the saw and switched to using gigantic robotic shears. Although the shears made an irregular cut, Allen told reporters he expects the seal to still be tight.

"We would have liked to have had the diamond cut ... because that gives you a smooth fitting that you can actually put a cap on ... with a rubber seal. This one is going to be a little looser fitting. There might be some oil escaping around the edges," Allen told "Good Morning America."

Once the new containment device is on, BP may need to go back down to make a cut with the diamond wire saw once it understands what is happening with the riser pipe, Allen said.

"For now, we need to contain this oil as quickly as possible," Allen said.