Gulf oil spill update: What's known now about cause and effects

Amid hearings on the cause of the Deepwater Horizon disaster, government scientists, academics, and those most affected by the Gulf oil spill are at odds over the extent of its effects.

The well responsible for the Gulf oil spill was permanently sealed on Sept. 19. Since then, little else regarding an event many consider the worst environmental disaster in American history has been so categorical.

The presidential commission investigating the accident is searching for what caused the explosion, but is not yet assessing blame. Government scientists are offering relatively positive observations about state of the Gulf, which are being vociferously questioned by some independent scientists and fishermen. The government also differs with oil industry economists on how much the now-ended moratorium on deep-water drilling hurt the Gulf economy.

The effects of the spill are so complex that they may not be fully known for years. But they are emerging.

IN PICTURES: Destructive oil spills

What is known about the cause?

Investigators know that a huge bubble of flammable methane gas escaped the well and ignited after shooting up the drill pipe, past several seals that were meant to suppress it. How and why the gas escaped is one focus of the presidential commission looking into the accident and its implications for offshore drilling.

The commission's final report is due Jan. 12. A second report, by the US Coast Guard and the Bureau of Ocean Energy Management, Regulation and Enforcement, will be available March 27.

So far, the three companies involved – Transocean (owner of the Deepwater Horizon rig), BP (holder of the lease for the well), and Halliburton (a contractor) – are engaged in a mutual blame game.

A BP report published in September suggests the explosion was the result of an interlinked series of missteps, including mechanical failures and human errors, among all partners. Transocean called the report "self-serving" and called BP's well design flawed. Halliburton said the report had "substantial omissions and inaccuracies."

Halliburton received its own share of blame in late October when the investigator for the presidential commission issued a report saying that the company had used a cement mixture it knew was unstable. The commission did not blame the accident on Halliburton's cementing job, though.

A lead investigator on the presidential commission reported this week that BP does not share sole responsibility for the accident, indicating that it was likely due to several missteps among all the partners. One example is the decision by BP and Transocean to operate the well after a pressure test suggested that it was not stable enough to handle the explosive gas and oil mixture.

Is the oil cleaned up?

The cleanup efforts – paid for by BP, directed by the US Coast Guard – continue in the Gulf, with about 9,200 workers and 200 local vessels. At the height of the crisis, more than 48,000 workers and 3,200 vessels were involved.

Oil is still being discovered along the shorelines of all four coastal states, even appearing in areas that were once cleaned, a frustrating situation caused by unpredictable tidal patterns.

In an Oct. 27 briefing, the oil spill response command said 93 miles of coastline had moderate to heavy oil. Two months earlier, on Aug. 24, that number was 135 miles.

There is no determination yet on how to define when the job will be finished. Officials say beach cleanup efforts will likely end by early 2011. But critics say that despite the cosmetic cleaning being performed by work crews, oil will continue to smear shorelines for the foreseeable future.

To date, BP has paid $11.6 billion in recovery costs, which includes cleanup and is part of the estimated $40 billion total it expects to pay.

What is the economic toll so far?

The oil spill particularly affected the tourism, seafood, and oil and gas industries of the Gulf Coast.

Revenue at Gulf Coast hotels in Alabama and the Florida panhandle dropped as much as 29 percent from 2009, according to the Santa Rosa Island Authority. But New Orleans expects its best tourist year since hurricane Katrina, and tourism in Florida is up 3.4 percent statewide.

For the seafood industry, only 4 percent of Gulf federal waters remained closed as of Oct. 29 – down from a high of 37 percent. But the spill could cost the seafood industry as much as $172 million from 2011 to 2013, according to a study by Greater New Orleans Inc., an economic development agency. The Louisiana Seafood Promotion and Marketing Board reports that demand outside the region remains low.

The oil and gas industry and state leaders, meanwhile, have been at odds with the federal government regarding the effects of the six-month moratorium on deepwater drilling. A US Commerce Department survey found that 2,000 people directly involved in the offshore industry lost their jobs. By contrast, a study by Louisiana State University economist Joseph Mason said 8,000 people lost their jobs, and more would follow.

Industry officials also note that though the moratorium was lifted early, the US has not yet issued any new deepwater permits, raising fears of long delays. Thirty-three deepwater drilling projects in the Gulf were shut down by the moratorium. Three have since relocated to other countries.

What about water quality and wildlife?

Some 5 million barrels (205 million gallons) of oil entered the Gulf. Where it all is now is a question that continues to be fiercely debated. Federal officials first argued that the "vast majority" of oil is gone, but then had to backtrack. Different teams of independent scientists have reported that as much as 80 percent of the oil remains.

Some is on the surface, with local fishermen insisting that huge patches of weathered oil were still floating off the coast Oct. 23. Government scientists said tests showed it was an algae bloom.

Similarly, independent scientists have said that oil remains on the ocean floor and suspended in the water column in plumes. Government scientists say they have found only trace amounts of undersea oil.

Nearly 7,000 animals have been found dead, which scientists say is probably a small portion of affected wildlife.