GWEN IFILL: Now to the latest on the oil spill in the Gulf of Mexico.
Engineers are on the brink of permanently killing the Macondo oil well and are set to begin tests tonight on procedures that will make that happen.
This weekend, "NewsHour" correspondent Tom Bearden visited the site of that well and reports on the efforts that one ship played in containing the oil.
TOM BEARDEN: The drill ship Discoverer Enterprise was at the center of the effort to choke off the red-brown gusher a pile beneath the surface of the Gulf. The operators of the ship's remotely controlled underwater vehicles tried a variety of containment domes, before finally finding the right combination of pipes and valves that, once bolted to the well, could stifle the high-pressure oil jet.
Jim Stewart is the ship's captain.
The perception of some us watching from shore was, you tried something. It didn't work. You tried something else. It didn't work.
JIM STEWART, captain, Discoverer Enterprise: True.
TOM BEARDEN: And you tried something else, and it still didn't work.
JIM STEWART: Yes.
TOM BEARDEN: At any point, did you ever think you couldn't do this?
JIM STEWART: No. You can't go into it thinking that way.
There were weeks of planning before anything really happened, as a lot of people probably wondered at home, what is taking so long? And the proper planning, over and over, with a lot of people, hours of conference calls took place, before we took action. And, once we did take action, it was successful, and it was because of all that planning.
JASON BRAQUET, offshore installation manager: This is what we call an executive walkway. It is an entry to the rig floor.
TOM BEARDEN: Offshore installation manager Jason Braquet took a group of journalists on a tour of the massive ship. It's capable of drilling two wells at once. So, there are stacks of steel pipes ready for use, cranes to move them, a towering derrick to hoist them into place.
Braquet says the crew is the elated that the job seems to be almost over.
JASON BRAQUET: Really good about this operation, and really good about what we accomplished. You know, we did this incident-free, with no harm to any -- any personnel out here. So, it is a good accomplishment.
TOM BEARDEN: Proud of it?
JASON BRAQUET: Damn proud of it. You don't see any oil out here, and it's -- it's great to know we enter the last stage of this operation.
TOM BEARDEN: Any doubt this is the last stage?
JASON BRAQUET: No. I think we're going to be successful. I'm pretty -- pretty -- really confident we're going to be successful.
TOM BEARDEN: Discoverer Enterprise is in standby mode right now. She has moved about a half-mile from the blown-out well. Another drilling platform called the Q4000 and two support vessels are in the final stages of preparing the so-called static kill.
Those vessels have the equipment to inject heavy drilling mud into the top of the well to push the column of oil back down the pipe, then inject a slug of cement to seal it permanently. But Discoverer Enterprise is ready to move in should there be a problem.
An eighth-generation containment cap dangles from a cable positioned just above the bottom. The crew is ready to put it into position should the well need to be sealed again.
Ron Bretzke pilots a remotely operated vehicle, or ROV, from a darkened room below decks. He keeps an electronic eye on the standby cap using a joystick and a throttle to control the machine. ROVs are the only way to work at depths that would instantly crush a human diver. He was part of the ROV crew that attached the cap that finally stopped the flow.
RON BRETZKE, ROV pilot: The most pressure is what we put on ourselves. I mean, granted, there was a lot -- a lot of people watching what we were doing. You know, a lot of people, a lot of eyes on, making sure we, you know, did it right. But I think the most pressure is what we put on ourselves.
TOM BEARDEN: Also feel a bit of relief?
RON BRETZKE: Oh, absolutely. Oh, that relief -- when they put that final cap on, hopefully, you know, and said that they have stopped the oil flow, I think everybody started breathing a little easier then.
TOM BEARDEN: It wasn't all done from an air-conditioned room, however. When the Discoverer Enterprise was connected to the containment cap and oil was still flowing, the ship collected large quantities of oil and natural gas. It had to flare off the gas by means of a boom projecting out over the water.
JASON BRAQUET: This was here was the flare boom. This is where we had the 50-to-100 foot flame burning, where we couldn't even have a conversation if -- because of the noise. It sounded like a big jet engine on the noise that was generated by that flame.
JIM STEWART: A 12-hour day in this heat, under the environment that we had here, I wish you could have seen that and heard it and felt it. The heat was not bearable. You could only work in that area so long and have to get out.
TOM BEARDEN: Even if the static kill is successful, BP and Transocean plan to complete one of the two relief wells they started drilling shortly after the blowout. The drilling platforms that are doing that work are anchored on either side of the original well.
The original plan had been to intersect the Macondo well casing 18,000 feet beneath the surface, then inject drilling mud and cement. BP officials said the exact procedure may change, but remain confident they will permanently seal the well.
GWEN IFILL: In Washington today, the Environmental Protection Agency defended BP's use of chemical dispersants to break up all that oil. Its study, which found the chemicals no more or less toxic to aquatic life than oil alone, came in response to critics who said BP overused thousands of gallons of the dispersant.