A second, smaller oil containment box was lowered into the sea near the blown-out well in the Gulf of Mexico.
The box was being slowly submerged to the seabed Tuesday. But it won't be placed over the spewing well right away. BP spokesman Bill Salvin says engineers want to make sure everything is configured correctly and avoid the same buildup of ice crystals that stymied their first attempt at using a larger box that was about 100 tons.
This box will be connected to a ship on the surface by a pipe-within-a-pipe when it's lowered. Crews plan to pump in heated water and methanol so ice won't build up.
Salvin said undersea robots will position the box over the gusher by Thursday.
More than 4 million gallons of oil have spewed from the well since a drilling rig exploded April 20. At that rate, the accident could eclipse the Exxon Valdez disaster by Father's Day.
BP attempted to install a massive containment device over the larger of two leaks on the sea floor to funnel oil to the surface for collection.
But after lowering the huge dome into the sea on Thursday night the company said Saturday that chamber was blocked by hydrates, or crystallized gas, and had to be removed.
The icelike hydrates are crystals formed at high pressure and low temperature where water and natural gas are found.
There will be less seawater in the smaller dome, which will reduce the chance of hydrate formation, BP said. Moreover, methanol will be injected into the chamber to try to prevent the formation of hydrates.
The original dome, which took about two weeks to build, was four stories high and weighed 98 tons. The smaller dome, which will be anchored to the sea floor with pipe, is four feet in diameter and five feet high, BP said.
The design for both calls for siphoning captured oil up to a ship via a milelong pipeline.
The company is also planning to try and block the crude flow with a "junk shot," in which materials including golf balls, knotted rope and shredded tires will be shot at high pressure into the well's failed subsea blow-out preventer.
That process will take about two weeks, BP said.
All of the techniques BP is trying have never been attempted at the water depths of this well, which is 5,000 feet below the surface and where equipment is being maneuvered with remotely controlled vehicles.
BP also drilling a relief well in order to take pressure off the gusher and then cap it permanently. But that effort is expected to take up to 80 more days.