Next Steps In Test Of BP Gulf Oil Cap

BP shut all three valves to close a new cap over its busted Gulf of Mexico well Thursday, stopping the flow of oil into the water for the first time since April. What's next?

THE TEST: BP plans to keep the cap closed for 48 hours to see if it can withstand the pressure of the oil without blowing a new leak in the well. Every six hours, they'll assess the pressure readings and other data to decide whether to continue. High pressure is good; low pressure indicates a possible leak in the well and BP could open the cap again.

WHAT CAN GO WRONG: A leak somewhere in the well's piping that extends down far into the earth could complicate the situation in two ways. Oil and gas could erupt into the sea floor and be harder to contain. Damage to the pipes underground could also make it harder to plug the well for good with cement and mud.

NEXT STEPS: After the test, it's not clear yet whether the oil will remain bottled in the cap or whether BP will chose to use the new device to funnel the crude into four ships on the surface.

ENVIRONMENTAL IMPACT: The fishing industry in particular has been buffeted by fallout from the spill. Surveys of oyster grounds in Louisiana showed extensive deaths of the shellfish. Large sections of the Gulf Coast - which accounts for 60 to 70 percent of the oysters eaten in the United States - have been closed to harvesting.