impact on the gulf coast, to the people, to the culture, we all understand the difficult times we're going through and what we didn't want to do is compound that problem by making an irreversible mistake. >> retired admiral allen says after getting the new info from b.p., he gave the go ahead to get this thing started. jonathan sierry live in grand isle, louisiana tonight. explain how this works and what the concerns are. >> certainly, shep. what they're doing right now is slowly closing the valves on that new cap on the well and then measuring the oil pressure that builds up inside. high pressure lets them know they're containing the oil inside the well. a low pressure reading would indicate that there might be leaks in the well elsewhere. the concern was, the federal government wanted assurances from b.p. that by increasing the pressure in that cap, that they weren't going to create additional ruptures inside that well, shep? >> this must be quite a relief for folks down there or is it? >> well, it is a relief but at the same time, the folks here have experienced countless delays and countless setbacks so