If both barrels fail there is the possibility of putting a new blowout preventer on top of the old one.

ECONOMIST: The Gulf oil spill

The goal of the hearings is to examine the design and performance of the drilling rig's blowout preventer, a mammoth set of valves that is the last line of defense against an oil spill.

WSJ: Transocean Cites Safety in Bonuses

On May 26th BP, the company responsible for the well that Deepwater Horizon had drilled, started to pump heavy drilling mud into the well's blowout preventer, a set of valves on the sea floor.

ECONOMIST: Nerves are fraying a month after the Gulf of Mexico oil spill