Gulf of Mexico oil reaches coast; White House calls spill event of "national significance"

the well. Such switches are not required in the United States, but are used in other countries such as Norway and Brazil.

Suttles said the rig was equipped with some safety devices that should have prevented this kind of spill. “They didn’t do that, we don’t know why they didn’t do that and ultimately we will find out,” he said.

Suttles was quick to point out that another company was operating the rig at the time of the explosion, not London-based BP. “I can say that we had equipment required by the regulations,” he said. “We don’t know why, when the accident occurred, and I should probably clarify, the lease we are drilling on is owed by BP and a few other companies.”

Parts of the massive spill were set on fire Wednesday as part of an experiment to try and stop the oil slick from reaching the coastline. Officials said the burn worked, but it was too windy today to try it again.

As the oil approached the coastline, biologists said it threatened as many as 400 species, including sea turtles and dolphins.

One ray of hope is that about 30 percent of an oil slick usually evaporates in the strong southern sun, and microbes and waves take care of another large portion. “Mother nature does a much better job at cleaning up than we do of picking up,” said Ed Levine, an oceanographer with the National Oceanographic and Atmospheric Administration.

The Deepwater Horizon drilling rig, operated by BP Oil and owned by Transocean Ltd., exploded and started burning April 20. Eleven rig workers were never found and are presumed to have died.

BP and its contractors are fighting a high-stakes battle to keep the spill from getting worse. They have tried, unsuccessfully so far, to cover the leaking wellhead with a dome or close it with a submersible robot.

Oil from the area is called light sweet crude, but Edward Overton, a professor emeritus of environmental science at Louisiana State University, said the name is deceptive. It contains heavy compounds, called asphaltenes, that do not burn easily or evaporate, even in the warm climate off Louisiana. “When you’ve got a spill like this,” said Overton, “there are three things you can do. You can burn it, scoop it up out of the water, or use chemical dispersants to break it up. This oil is not particularly good with any of those three.”

“With light crude,” he said, “you could burn most of it — 70 or 80 percent. With heavy crude, I don’t know. I’m not optimistic.”