US Coast Guard sets fire to giant oil slick as it nears Louisiana

The US Coast Guard set fire to parts of a growing oil slick in the Gulf of Mexico last night in a desperate effort to keep it from reaching shore and hopefully avert an ecological calamity.

It was the first time a controlled burn of this kind had been attempted off the US shoreline. "Right now, it's a test burn. We're trying to see how it works," Chief Petty Officer Steve Lehmann said. "We want to make sure we do it right. You need to herd it up and group it a certain way, and then there's the whole lighting of it."

The slick, created by the explosion and fire that consumed a rig operated by British Petroleum over a week ago, is posing an increasingly grave risk to an area of the Louisiana coastline, where the Mississippi River empties into the ocean, that contains no less than 40 per cent of all the country's wetlands.

"If some of the weather conditions continue, the Delta area is at risk," warned Charlie Henry of the National Oceanic and Atmospheric Administration. The oil is about 20 miles away from the Louisiana shore. But with more gushing from a broken well pipe almost 5,000ft below the ocean surface, at the rate of roughly 42,000 gallons a day, there seemed little doubt that the slick would expand and eventually touch land somewhere along the Gulf coast, an area especially rich in bird and fish species.

"It's going to happen," one US official said. By most recent estimates, the slick had grown to cover an area of 2,138 square miles.

Eleven lives were lost when the rig, owned by a Swiss company, Transocean, and operated by BP, exploded last Tuesday. The rig eventually collapsed and sunk into the ocean. It took until Saturday for engineers to discover the leak of oil from the well pipe. A BP disaster team has been trying since then to use robotic submersible craft to install a device on the seabed that would shut off the flow of oil, but so far the operation has been unsuccessful.

It is only the thickest of the surface oil that can be separated off from the larger slick and set on fire. Each controlled burn is scheduled to last 60 minutes or less. "When you can get oil ignited, it is an absolutely effective way of getting rid of a huge percentage of the oil," noted Greg Pollock, of the Texas General Land Office which has loaned equipment for the operation.

"I can't overstate how important it is to get the oil off the surface of the water."

Hardened tar balls would remain after the burning, which could be removed from the water using nets or skimmers. "I would say there is little threat to the environment because it won't coat an animal," Mr Pollock said.

Political pressure was meanwhile growing for a full explanation from BP of what happened at the rig. Officials have reacted angrily to reports that BP resisted an attempt by the US government last year to instigate tough rules and regulations for offshore drilling, insisting at the time that the voluntary guidelines in place were sufficient.

In Washington, officials confirmed that a federal investigation into the circumstances of the rig explosion would be undertaken and would include provisions for issuing subpoenas to compel corporate officers to testify.

With little to indicate that the submersibles would succeed in stopping the leaks, BP was exploring other options. That includes installing some form of tent or solid dome over the area of the leak, also something that has never been attempted at so great a depth. And equipment is in place to begin drilling a new hole into the crippled well with a view to injecting fluids including concrete eventually to seal it. But that would take months.

*The US government last night said it had given final approval for America's first offshore wind farm. After almost nine years of controversy, construction can now start on an array of turbines in waters off Cape Cod and the island of Nantucket. Among those who had opposed the farm was the Kennedy family and a local Indian tribe. The Kennedy family home at Hyannis Port – where Senator Edward Kennedy lived until his death in 2009 – consists of six acres of waterfront property on Cape Cod along Nantucket Sound.