Chris in Paris (AMERICAblog):
The concern with the latest BP attempt to stop the massive leak has been that the pressure of shutting well down could force the sea floor to rupture and create an even larger problem. Observers had been closely following the valve pressure which would indicate whether or not there was a leak elsewhere. It now sounds as though US officials were not seeing enough pressure in the valve which suggests a leak somewhere else. If the well starts leaking elsewhere that could become a substantial problem. Opening new leaks beyond the well will be difficult to shut down. After the painful start to this disaster by the US government, it is good to see them paying more attention and finally, giving orders. BBC:BP had hoped the cap could stay in place until relief wells stop the leak for good.
But with pressure readings from within the well lower than expected, scientists had raised concerns that oil could leaking into the surrounding undersea bedrock.
And in a letter to BP chief managing director Bob Dudley, Admiral Allen said: "Given the current observations... including the detected seep a distance from the well and undetermined anomalies at the well head, monitoring of the seabed is of paramount importance...
"I direct you to provide me a written procedure for opening the choke valve as quickly as possible without damaging the well should hydrocarbon seepage near the well head be confirmed."