New Orleans, La. – Retired Coast Guard Admiral Thad Allen says the new cap will take pressure readings. If they're too low, it means there could be other breaks in the well and plugging oil from the top could trigger more leaks. If they're high enough, valves on the cap will gradually be shut off. Allen says he's very confident the cap will stay in place. If it's not able to stop oil from flowing out it will at least be able to funnel it to surface ships.
"We could do it through a potential shut-in of the well or being able to produce most if not all of the flow that we believe is generated, either way, we will have a way to contain the oil."
Pressure readings starting today could take 48 hours to complete. Energy Secretary Steven Chu is in Houston, overseeing the operation.
For NPR News, I'm Eileen Fleming in New Orleans.