...it reached the coast, BP worked on multiple fronts to stem the flow. “The first thing is to stop this thing at the source,” says Coast Guard Adm. Thad Allen, tapped on May 1 by the Obama administration to coordinate the joint-task-force response to the spill. “To continue to fight this thing on the surface and shore is not the way to do it.” The JTF deployed nine remotely operated vehicles (ROV) to the seafloor to assist in stopping the oil flow.

For more than a week after the explosion, BP’s efforts focused on activating a blowout preventer, manufactured by Houston-based Cameron International, that was placed on top of the well during drilling. The 450-ton, 40-ft-high, 16-ft-wide BOP has hydraulically operated rams that, when activated, act as a shut-off valve for the 5- to 7-inch riser pipe. One of the rams is a shear, which cuts the pipe to stop the flow of oil and gas. The safety devices, which are rated to at least 15,000 psi, are designed to activate when turned on from a rig above or when power is lost, says Danenberger. The BOP was tested 10 days before the explosion. On May 3, Suttles said that tests performed by the ROVs indicate the BOP was at least partially activated; BP believes oil is leaking from its seals.

Focusing on other options, BP is now considering removing the faulty BOP and installing another. The company also said on May 3 that it expects to deploy a containment dome over one of the leaks within a week. The 98-ton box, being built by Houston-based Wild Well Control Inc., Port Fourchon, La., would capture the oil floating to the surface and pipe it to a Transocean drill ship that can hold 125,000 barrels of oil. That method has been used in shallower waters.

“The real problem is the engineering associated with that and how to mechanically accomplish that 5,000 ft down,” Allen says. ROV operators are currently pursuing another option: crimping and cutting the leaking riser pipe. That solution would lessen, but not stop, the flow.

Suttles, Allen and others say the most likely way to stop the oil is by drilling a relief well—a 90-day process­—and plugging the hole in the existing well.

Above the oily Gulf waters, planes dropped more than 156,000 gal of dispersant into the slick. The proprietary chemical mix acts like soap and breaks down the oil on and below the surface into less harmful molecules. The dispersants have toxic qualities, says Thomas, “but we’ve got to get rid of this oil.”

The JTF deployed a 200-vessel remediation fleet, including surface-skimmer boats. As of May 4, they had retrieved more than 1 million gal of oil and water.

The week of May 3, favorable winds were keeping most of the oil from reaching land; the estimated size of the oil sheet shrank, to 2,000 sq miles from 3,400 sq miles. The Mississippi’s flow is keeping the spill east of the river mouth, and some scientists worry that the farther south and east the oil moves, the more likely the spill could hit the Gulf Stream and make its way up the East Coast.