The effort could continue through Thursday, and engineers won't know for more than a week if it choked the well once and for all.
"This is a really positive step forward," said retired Coast Guard Adm. Thad Allen about the operation. "It's going to be good news in a time where that hasn't been very much good news, but it shouldn't be a cause for premature celebration."
The static kill operation is meant as insurance on top of what's already in place - the experimental cap that has held for more than two weeks. The cap was never meant to be permanent.
The testing was supposed to be wrapped up by Monday, but a minor leak in the hydraulic control system delayed the test until Tuesday. Since then, the leaks have been fixed and the operation is set to begin on Tuesday afternoon.
BP officials said that the static kill operation may plug the oil leak completely, but the company said there's no way to tell until the relief wells are completed.
Allen said that finishing the relief wells is the only surefire way to make certain the well is permanently plugged. The static kill process will take days to compete due to the slow speed the mud will be pumped into the well. However, Allen said that crews will be able to know within hours if the process is working.
Tropical Storm Colin formed far out in the Atlantic on Tuesday, but it is forecasted to go toward the East Coast rather than the Gulf. Still, Allen emphasized the importance of beginning the static kill operation soon, with the peak hurricane season just around the corner.
- A federal task force said Monday that about 172 million gallons of oil made it into the Gulf between April and July 15, when the temporary cap contained all the oil.
The task force said about 206 million gallons actually gushed out of the well, but a fleet of boats and other efforts were able to contain more than 33 million. The 172 million gallons is on the high end of recent estimates that anywhere from 92 million to 184 million gallons had gushed into the sea.
- Judging by the latest estimate, BP could be fined up to $5.4 billion under the Clean Water Act, or as much as $21 billion if it is found to have committed gross negligence or willful misconduct. The high-end fine would drop to around $17.6 billion if the government credits BP for the oil it has recovered, while the low-end fine would be around $4.5 billion.
- BP and federal officials have managed to contain large parts of the spill through skimmers, boom and chemical dispersants meant to break up the oil. Federal regulators have come under fire from critics who say that BP was allowed to use excessive amounts of the dispersants, but government officials counter that they have helped dramatically cut the use of the chemicals since late May.
The Environmental Protection Agency released a study Monday concluding that when mixed with oil, chemical dispersants used to break up the crude in the Gulf are no more toxic to aquatic life than oil alone.
The Associated Press contributed to this report.