Oil is now flowing into the Gulf without being collected from the well head. Oil is expected to gush freely into the water for about 48 hours until the new cap is installed. This window is long enough for as much as 5 million gallons of oil to gush out.
The goal for the new lid is to funnel more oil to collection ships on the surface a mile above. The surface ships coupled with the new cap could keep all the oil from polluting the fragile Gulf as soon as Monday.
"Over the next four to seven days, depending on how things go, we should get that sealing cap on. That's our plan," Kent Wells, a BP senior vice president, said Saturday as he explained the procedure.
It would be only a temporary solution to the catastrophe unleashed by a drilling rig explosion nearly 12 weeks ago. It won't plug the busted well and it remains uncertain that it will succeed.
The best hope for a permanent solution remains with two relief wells intended to plug the leak once and for all, far beneath the seafloor.
Coast Guard officials said Saturday that it could still be another week before they really know if the cap is containing most of the spill. Testing has to be done on the new cap if and when it's in place to make sure it can withstand the pressure of the gushing oil.
Workers are taking advantage of a window of good weather following weeks of delays caused by choppy seas.
The cap now in use was installed June 4, but because it had to be fitted over a jagged cut in the well pipe, it allows some crude to escape. The new cap - dubbed "Top Hat Number 10" - follows 80 days of failures to contain or plug the leak.
Containing the leak will not end the crisis that began when the Deepwater Horizon drilling platform exploded April 20, killing 11 workers. The relief wells are still being drilled so they can inject heavy mud and cement into the leaking well to stop the flow, which is expected to be done by mid-August. Then a monumental cleanup and restoration project lies ahead.
- Friday, BP worked to hook up another containment ship called the Helix Producer to a different part of the leaking well. The ship will be capable of sucking up more than 1 million gallons a day when it is fully operating.
- The government estimates 1.5 million to 2.5 million gallons of oil a day are spewing from the well, and the existing cap is collecting about 1 million gallons of that. With the new cap and the new containment vessel, the system will be capable of capturing 2.5 million to 3.4 million gallons - essentially all the leaking oil, officials said.
The Associated Press contributed to this report.