What had been thought to be the best immediate solution to contain the leak, a 78-ton steel and concrete box known as a cofferdam that took two weeks to build, rested useless on the seafloor, and the gulf’s fragile ecosystem seemed to be facing if not the worst case scenario, then one that was certainly very bad — an outpouring of oil that will go on for perhaps three more months before a relief well can intercept the leaking one and seal it.

A top Coast Guard official suggested that experts might try to cork one of the two existing leaks by stuffing shredded tires, golf balls and other debris into the well’s failed blowout preventer. But it was uncertain how seriously that option was being considered; executives of BP, the leaking well’s owner, said earlier in the week that such a move could make things worse by damaging whatever part of the blowout preventer was still working.