Engineers were today preparing to test a new cap designed to stop the BP oil leak.
They first had to fix a broken pipe on the new device which delayed the operation.
The main test will involve closing all three openings in the cap to the Gulf of Mexico, in theory stopping the oil flow completely.
BP expects to keep the oil trapped for 48 hours before it decides if the approach is working.
The cap – a 75-ton metal stack of lines and valves – was lowered onto the well on Monday in hopes of either bottling up the oil inside the well machinery, or capturing it and funnelling it to the surface.
Having replaced the broken pipe, BP has to start from a few steps back to resume the process of testing the cap’s ability to shut off the flow of oil to the Gulf.
It has to once again stop the collection of oil from surface vessels, which resumed after the leak was discovered.
Then it has to recheck equipment used in the test and move undersea robots that perform the work back into position.
A spokesman expected the test to start on Monday, possibly late in the morning.
Retired Coast Guard Adm. Thad Allen, the US government’s representative, said a committee of scientists and engineers will monitor the results and assess every six hours, and end the test after 48 hours to evaluate the findings.
“I was gung-ho for this test and I remain gung-ho for this test,” he said .
If the cap works, it will enable BP to stop the oil from gushing into the sea, either by holding all the oil inside the well machinery like a stopper or, if the pressure is too great, channelling some through lines to as many as four collection ships.
Adm. Allen said the testing will also offer insight into the other, more permanent solution to the fix: two relief wells intended to plug the leak from deep underground. The mapping of the sea floor that was done to prepare for the well cap test and the pressure readings will also help them determine how much mud and cement will be needed to seal off the well.
Drill work was stopped on one relief well because it was not clear what effect the testing of the cap could have on it. Work on the other relief well had already been stopped according to plan.
The US government estimates up to 2.5 million gallons are leaking every day.
The crisis began April 20 when the BP-leased Deepwater Horizon rig exploded, killing 11 workers.
In the 12 weeks since, an estimated 92 million gallons to 182 million gallons of oil have flowed into the Gulf.