Oil is no longer spewing into the Gulf of Mexico as BP choked off the flow from its ruptured undersea well. But this is only a temporary solution. The company hopes it will be able to conduct a "static kill" of the well, which should seal it for good.
Millions of gallons of oil had poured into the Gulf beginning with an explosion on April 20 of the Deepwater Horizon oil rig that killed 11 workers and led to an economic and environmental catastrophe along the U.S. Gulf Coast. The huge spill has soiled hundreds of miles of coastline, and threatens a fragile ecosystem.
Below is a timeline of the spill and its impact:
April 20, 2010—Explosion and fire on Transocean's drilling rig Deepwater Horizon licensed to BP ; 11 workers are killed. The rig was drilling in BP's Macondo project 42 miles southeast of Venice, Louisiana, beneath about 5,000 feet of water and 13,000 feet under the seabed.
April 22—The Deepwater Horizon rig, valued at more than $560 million, sinks and a five mile long oil slick is seen.
April 25—The Coast Guard says remote underwater cameras detect the well is leaking 1,000 barrels of crude oil per day. It approves a plan to have remote underwater vehicles activate a blowout preventer and stop leak. Efforts to activate the blowout preventer fail.
April 28—The Coast Guard says the flow of oil is 5,000 barrels per day (bpd) (210,000 gallons/795,000 litres)—five times greater than first estimated. A controlled burn is held on the giant oil slick.
April 29—Obama pledges "every single available resource," including the U.S. military, to contain the spreading spill. Obama also says BP is responsible for the cleanup. Louisiana declares state of emergency due to the threat to the state's natural resources.
April 30—An Obama aide says no drilling will be allowed in new areas, as the president had recently proposed, until the cause of the Deepwater Horizon accident is known. BP Chairman Tony Hayward says the company takes full responsibility for the spill and would pay all legitimate claims and the cost of the cleanup.
May 2—Obama visits the Gulf Coast to see cleanup efforts first hand. U.S. officials close areas affected by the spill to fishing for an initial period of 10 days. BP starts to drill a relief well alongside the failed well, a process that could take two to three months to complete.
May 5—A barge begins towing a 98-ton containment chamber to the site of the leak. BP says one of the three leaks has been shut off by capping a valve, but that would not cut the amount of oil gushing out.
May 6—Oil washes ashore on the Chandeleur Islands off the Louisiana coast, uninhabited barrier islands that are part of the Breton National Wildlife Refuge.
May 7—BP tries to lower a containment dome over the leak, but the 100-ton device was rendered useless by a slush of frozen hydrocarbons that clogged it. A fishing ban for federal waters off the Gulf is modified, expanded and extended to May 17.
May 9—BP says it might try to plug the undersea leak by pumping materials such as shredded up tires and golf balls into the well at high pressure, a method called a "junk shot."
May 11/12—Executives from BP, Transocean and Halliburton appear at congressional hearings in Washington. Senate Energy committee chairman Jeff Bingaman says that it appeared that the explosion on the rig was due to a "cascade of errors, technical, human and regulatory. The executives blame each other's companies.
May 14—Obama slams companies involved in the spill, criticizing them for a "ridiculous spectacle" of publicly trading blame over the accident in his sternest comments yet.
May 16—BP succeeds in inserting a tube into the leaking well and capturing some oil and gas.
May 18—The U.S. nearly doubles a no-fishing zone in waters affected by the oil, extending it to 19 percent of U.S. waters in the Gulf.
May 19—The first heavy oil from the spill sloshes ashore in fragile Louisiana marshlands and part of the mess enters a powerful current that could carry it to Florida and beyond.
May 26—A "top kill" maneuver starts involving pumping heavy fluids and other material into the well shaft to stifle the flow, then sealing it with cement.
May 28—Obama tours the Louisiana Gulf coast on his second visit. "I am the president and the buck stops with me," he said. BP CEO Tony Hayward flies over the Gulf. BP says that the cost of the disaster so far is $930 million.
May 29—BP says the complex "top kill" maneuver to plug the well has failed, crushing hopes for a quick end to the largest oil spill in U.S. history already in its 40th day.
May 31—The U.S. government and BP are warning that the blown-out oil well may not be stopped until August as the company prepares a new attempt to capture leaking crude.
June 1—BP shares plunge 17 percent in London trading, wiping $23 billion off its market value, on news its latest attempt to plug the well has failed.
June 2 — BP continues work on a new plan to try to capture most of the escaping oil. This involves using robot submarines to cut off what is left of the leaking riser pipe, then lowering a containment cap over the wellhead assembly. Some difficulties are encountered with the cutting operation. — U.S. authorities expand fishing restrictions to cover 37 percent of U.S. federal waters in the Gulf.
June 3 — After previous sharp declines, BP shares rise more than 3 percent on market hopes that the latest plan to control the leaking well may make some progress. The six-week-old crisis has wiped a third off BP's market value since it began.
June 4 — BP's containment cap is said to be collecting about 1,000 barrels per day. The government estimates 19,000 barrels a day could be gushing.
June 6 — BP say its latest effort had captured 10,500 barrels of oil (439,950 gallons/s) in 24 hours and a second containment system should soon enable it to control the vast majority of oil.
June 7 — BP, which says it has now spent $1.25 billion on the spill, sees shares gain on news of the progress in containing the leak but still faces tough questions from investors and U.S. lawmakers.
June 8 — Obama says he wants to know "whose ass to kick" over the spill, adding to the pressure on BP. In an TV interview Obama also says that if Hayward worked for him, he would have fired him by now.
June 9 — BP efforts to stop the oil spill are to come under U.S. congressional scrutiny.
June 10 — In his first comments, Prime Minister David Cameron says Britain is ready to help BP deal with the spill.
June 11 — Supportive comments from Britain lift BP's shares in London by 6.4 percent. But the rise does not mend the damage done—the company is worth 70 billion pounds ($102 billion) against more than 120 billion pounds in April.
June 14 — Obama, on his fourth trip to the Gulf, says he will press BP executives at a White House meeting on June 16 to deal "justly, fairly and promptly" with damage claims.
June 15 — Lawmakers summon top executives from Exxon Mobil , Chevron , ConocoPhillips , Royal Dutch Shell and BP.
June 16 — BP agrees to set up a $20 billion fund for damage claims from the spill, suspends dividend payments to shareholders and says it will pay $100 million to workers idled by the six-month moratorium on deep-sea drilling.
June 17 — Hayward faces the wrath of U.S. lawmakers as he appears before a congressional hearing. He apologizes for the spill and says everything is being done to stop it. Members of Congress accuse BP of cutting corners and ignoring warnings for the sake of profit.
June 18 — Anadarko Petroleum , part owner of the gushing well, says BP's behavior before the blowout was "reckless" and likely represented "gross negligence or willful misconduct" that would affect obligations of the well owners under their operating agreement.
June 22 — Hayward is handing day-to-day control of the spill operation to Bob Dudley — a reflection, says BP, of the need for the chief executive to return to other aspects of the energy giant's business.
June 24 — A U.S. judge refuses to put on hold his decision to lift a ban on deepwater drilling imposed in response to the spill.
June 27 — Oil washes ashore on mainland Mississippi for the first time, although some had tainted its barrier islands.
June 28 — BP is forced to defend its chief executive after Russia's deputy prime minister said he expected Hayward to resign soon.
June 29 — BP said that its oil-capture systems at the leaking well in the Gulf of Mexico collected or burned off 25,220 barrels of oil on Tuesday.
June 30 — Rough weather whipped up by the season's first Atlantic hurricane is disrupting cleanup of the massive BP oil spill in the Gulf of Mexico, delaying plans to boost containment capacity and threatening to push more oily water onshore.
June 30 — Hurricane Alex, later downgraded to a tropical storm, moved slowly inPTKwaters, disrupting the cleanup, and threatening to push more oily water onshore.
July 1 — BP shares gain, with traders initially citing talk, quickly shot down, that it had capped the leaking well.
July 3 — A supertanker converted into a "super skimmer" begins tests. The vessel can remove up to 500,000 barrels (21 million gallons/79.5 million liters) of oil and water from the sea surface a day.
July 5 — BP says that the cost of the spill had reached $3.12 billion.
July 6 — Summer storms push oil from the Gulf of Mexico spill deeper into Louisiana's wetlands and temporarily slow efforts to contain damage.
July 7 — Tests show tar balls washed up on the Texas coast are from the spill, meaning every U.S. Gulf state — Louisiana, Mississippi, Alabama, Florida and now Texas — has been soiled by the spill.
July 8 — A U.S. appeals court deals the Obama administration a setback as it refuses to halt deepwater oil drilling.
July 10 — BP remove a containment cap from the oil well in the first step toward installing a bigger cap.
July 11 — BP say it is making progress on a new system to capture almost all the leaking oil.
July 12 — BP installs a "capping stack,'' which has a better seal than the last cap placed on the well and aims to stop oil from spewing out.
BP starts shutting a sequence of valves after getting approval from the U.S. government, delaying testing by 24 hours on fears the process could irreparably damage the well. BP starts a critical pressure test to gauge pressure in the well on July 14.
July 15 — BP says it has stopped the leak—at least during testing—with the new tight-sealing containment cap.
July 16 — The company carries out tests on whether the well remains intact as it moves to plug the leak permanently with the relief well intended to intersect the ruptured well and and seal it with mud and cement in August.
July 19 — BP says it has spent $3.95 billion so far on efforts to tackle its leaking well.
July 20 — BP says it has reached a deal to sell $7 billion in assets to Apache Corp as it raises money to cover costs related to the spill.
July 23 — BP says it is temporarily suspending relief well activities due to the approach of Tropical Storm Bonnie.
July 27 — BP names American Bob Dudley as its next CEO, saying Tony Hayward will stand down on Oct. 1.