ON THE GULF OF MEXICO — BP said Monday it hopes to drop a smaller containment chamber on the oil gusher by Thursday, and in the meantime it is again using chemicals sprayed at the bottom of the seafloor and also hopes to burn some oil off on Tuesday — the same day lawmakers start hearings into the disaster.
BP received Environmental Protection Agency approval and began pumping dispersant early Monday on the main leak a mile below sea level.
Sprayed by a remote-controlled submarine, the dispersants had never been tried at such depths before this spill and officials have been worried about the effect on the environment.
Officials have been encouraged by underwater spraying last week, saying it prevents some of the oil from reaching the surface.
Engineers at BP were also wrestling with a shopping list of ways to plug the well or siphon off the spewing crude, including a five-foot-tall containment box, dubbed a top hat, and injecting debris including shredded rubber into the well as a stopper, called a junk shot.
"The issue is how to keep some of the water out," BP Chief Operating Officer Doug Suttles told NBC's "TODAY" show on Monday. The top hat, he said, "is a much smaller dome" than the failed chamber attempted over the weekend.
"And in addition it has the ability to inject methanol into the top of it, which should prevent the hydrates from forming," Suttles said, referring to the icelike crystals that formed on the larger chamber, blocking the oil from being siphoned up.
Asked if BP was operating without a playbook in looking for options, Suttles said that "there's a lot of techniques available to us. The challenge with all of them is, as you said, they haven't been done in 5,000 feet of water."
The top hat strategy, BP CEO Tony Hayward told reporters later Monday, should be ready for deployment by Thursday.
On Monday, BP said that the spill has cost it $350 million so far, suggesting the final bill could be much higher than many analysts predicted. In a statement, the firm said the sum referred to the cost of spill response, containment efforts, relief well drilling, payments to the Gulf Coast States to speed up their response plans, some compensation claims and federal costs.
The company's shares was lower again on Monday. The stock has lost 16 percent since the Deepwater Horizon rig caught fire with the loss of 11 lives, wiping around $30 billion off BP's market value.
Big problem for BP
The cold, pitch-black depth of the seafloor is a formidable problem. That's where icy slush formed inside a a four-story container and foiled plans to funnel the oil to a surface tanker, which had been the best hope for containing the leak quickly while a drill rig spends up to three months boring a new well to shut down the old one permanently.
Video: BP's safety record far from clean The engineers appear to be "trying anything people can think of" to stop the leak, said Ed Overton, a LSU professor of environmental studies.
On land, helicopters dropped sandbags in Louisiana to guard against thick blobs of crude that began washing up on beaches as the well spills at least 200,000 gallons of oil a day into the Gulf.
The Army National Guard airlifted them to five spots along a four-mile stretch of coastline between Port Fourchon and the Jefferson Parish line, said Lafourche Parish compliance officer Robert Passman.
"We want to block it off to where the oil doesn't get into the marsh areas," said Passman. "What they're trying to do is just prevent. I know it's still east of here but they're just trying to do a little prevention."
Among plans under consideration for the gusher, BP is looking at cutting the riser pipe, which extends from the well, undersea and using larger piping to bring the gushing oil to a drill ship on the surface, a tactic considered difficult and less desirable because it will increase the flow of oil.
Video: Google Maps charts oil spill's growth A junk shot would be followed by cement to seal the leak and the technique is something company officials said they might try next week. The smaller container, or top hat, could be tried first, around the middle of this week.
An estimated 3.5 million gallons of oil have spilled since an explosion on April 20 on the drilling rig, the Deepwater Horizon, 50 miles off the Louisiana coast. At that pace, the spill would surpass the 11 million gallons spilled in the Exxon Valdez disaster by next month.
Above the oil leak, waves of dark brown and black sludge crashed into the support ship Joe Griffin. The fumes there were so intense that a crew member and an AP photographer on board had to wear respirators while on deck.
Philip Johnson, a petroleum engineering professor at the University of Alabama, said cutting the riser pipe and slipping a larger pipe over the cut end could conceivably divert the flow of oil to the surface.
"That's a very tempting option," he said. "The risk is when you cut the pipe, the flow is going to increase. ... That's a scary option, but there's still a reasonable chance they could pull this off."
Johnson was less optimistic that a smaller containment box would be less susceptible to being clogged by icelike crystals.
"My suspicion is that it's likely to freeze up anyway," he said. "But I think they should be trying everything they can."
New sense of urgency
There was a renewed sense of urgency as dime- to golfball-sized balls of tar washed up Saturday on Dauphin Island, three miles off the Alabama mainland at the mouth of Mobile Bay and much farther east than the thin, rainbow sheens that have arrived sporadically in the Louisiana marshes. Until Saturday none of the thick sludge — those indelible images from the Valdez and other spills — had reached shore.
The containment box plan, never before tried at such depths, had been designed to siphon up to 85 percent of the leaking oil to a tanker at the surface. It had taken about two weeks to build it and three days to cart it 50 miles out and slowly lower it to the well.
Slideshow: Oil disaster Icelike hydrates, a slushy mixture of gas and water, clogged the opening in the top of the peaked box like sand in a funnel, only upside-down.
The blowout aboard the rig, which was being leased by BP, was triggered by a bubble of methane gas that escaped from the well and shot up the drill column, expanding quickly as it burst through several seals and barriers before exploding, according to interviews with rig workers conducted during BP's internal investigation. Deep sea oil drillers often encounter pockets of methane crystals as they dig into the earth.
Lane Zirlott, 32, a commercial fisherman from Irvington, Ala., said he's not frustrated about BP failing so far to cap the leak because he understands how difficult the job is.
"When they said they were going to put this little cap over this thing, I laughed and said there's no way," he said. "I said there's no way they're going to do that. And then sure enough, it didn't happen."
The Associated Press contributed to this report.