With the replacement of the failed blowout preventer and a cement plug in place, the well's seal is almost permanent, the federal spill response chief says. The final step will be to plug the well from the bottom. With a new blowout preventer in place and a 5,000-foot column of cement filling its core, the BP well is no longer in danger of leaking oil, the federal spill response chief said Saturday — although he said it must still be plugged from the bottom for the job to be complete.