Whatever it takes: BP will go ahead with drilling a relief well to make sure the capped leak stays that way. The “static kill” operation successfully stopped the oil from spewing into the Gulf, and last week retired Coast Guard Adm. Thad Allen said a relief well might not be necessary—but scientists are reluctant to claim victory just yet. They’re nervous that the bottom plug of the well’s outer ring could be too thin and fragile. An added worry is that the static kill operation might have gone too well—the cement was pushed into the oil reservoir, trapping some oil between the bottom and the cap. Engineers, concerned that the added drilling mud and cement from the relief well might put so much pressure on that trapped oil that it damages the cap or bottom seal, are debating how to go ahead without creating more problems.