those are the mechanisms that control the blow-out preventer. if they don't work, the blow-out preventer doesn't work. a leak, even if only a trickle, is a warning. >> yeah. it's abnormal. >> abnormal enough that you reported it to your company, to transocean, to bp? >> that's correct. >> one pod is always working. the other, says university of texas petroleum engineer tad patzek, is designed as its immediate backup. >> i don't think there's any discussion of that basic fact. and the basic fact is that you have to do whatever it takes to fix fully the blow-out preventer as soon as you can. >> patzek says the solution is to immediately close off the well, raise the blow-out preventer, found out what's wrong and fix it. >> anything less than that, you know, might have led or probably led to a major failure of the well and the results are well known. >> back on board the deepwater horizon, several weeks before