Impact of Gulf oil leak 'could be immense'

With more oil than previously estimated leaking from below a Gulf of Mexico oil rig, Channel 4 News science correspondent Julian Rush says the environmental impact could be huge.

The US coastguard confirmed that London based BP Plc, who are financially responsible for the cleanup, found a third leak in a well 5,000 feet under the sea off Louisiana's coast.

Heading up the cleanup, US Coastguard Rear Admiral Mary Landry said: "BP has just briefed me of a new location of an additional breach in the riser of the deep underwater well."

Eleven workers are missing and presumed dead following the worst oil rig disaster in almost a decade.

The Deepwater Horizon, owned by Swiss based Transocean Ltd, sank on April 22, 36 hours after an explosion ripped through the rig which caught fire.

President Barack Obama has been briefed on the situation and help is being sought from the US defence department.

The leak, now estimated at 5,000 barrels per day, threatens coastal wildlife, pristine beaches and estuaries in Louisiana, Mississippi, Alabama and Florida.

Julian Rush reports
With the winds forecast to shift to the south-east, oil engineers are in a race against time to prevent the growing oil slick from hitting the Louisiana shore near New Orleans.

At its closest, the slick is only 16 miles from the coast, and it is forecast to come ashore by Friday. The outflow of water from the huge river may push some of it back but no-one's pretending the environmental impact won't be immense - the fragile ecosystem of the Mississippi River delta is very delicate.

NASA satellite imagery shows the Gulf of Mexico oil spill.

Three weapons are being used in the operation to deal with the leaking oil.

First, in a bid to reduce the amount of oil floating on the surface so less comes ashore, they have set light to some of it. Oil that is at least several millimetres thick is corralled into a fire resistant boom, towed away from the spill, and then ignited, leading to what they call a "controlled burn" of several thousand gallons of oil lasting approximately one hour.

The burn can be stopped at any time by opening the boom and allowing the oil to spread too thin for combustion.

Second, the efforts continue to activate the 'blow out preventer' on the well head. It consists of huge steel shutters that slice through the pipe to stop the flow. They're meant to be fail-safe: normally they are held open by huge hydraulic rams; in the event of a failure they should slam shut.

When the rig blew, it seems there was no time to operate them and no-one knows why they didn't activate automatically. Remote operated vehicles are being used to try to operate them manually but with no success so far.

Finally there's the long term solution. A second drilling rig is now on site and will "spud" this weekend (start drilling). The aim is to drill down to meet the existing well in the seabed beneath the well head, to divert the flow and cap it again.

It's been done often enough before, but it's difficult - they have to drill down and sideways for several thousand feet to hit a target that is two feet wide, several hundred feet underground. And it will take at least a month.

A mass oil sheen has already been created by the leak on the surface of the sea. The crude slick is now almost the size of the US state of West Virginia, and BP and the coastguard are desperate to contain it before it reaches land.

BP says its the largest oil spill containment operation in history, involving dozens of ships and aircraft.

Underwater robots failed to activate a cutoff valve on the ocean floor which would have plugged the leak. Now BP and the coastguard have set a "controlled burn" to battle the giant slick and prevent it from growing.

Head of group media at BP, Andrew Gowers said: "We will not rest until we have done everything to bring this under control." 

The threat now is that a shift in winds could push the spill inland to the Louisiana coast by the weekend. It is already only 23 miles off the coast.

The National Oceanic and Atmospheric Administration warned that tarballs and emulsified oil streamers could reach the Mississippe Delta late on Friday.

This would put at risk a large seafood industry as the area contains key wildlife habitats in the Pass-A-Loutre Wildlife Management Area and Breton National Wildlife Refuge.

Fishermen and oystermen rely heavily on the estuaries and swamps along the Mississippi river. President of the Louisiana Oysterman Association Byron Encalade lost five boats when Hurricane Katrina hit in 2005.

He said: "We're sitting here half praying and half with our fingers, toes and everything else crossed."

The Louisiana accident is the worst oil rig disaster since 2001, when a rig operated by Petrobras off the Brazilian coast exploded and killed 11 workers.

So far the spill is not nearly as big as the Exxon Valdez disaster, which spilled about 11 million gallons of oil into the Prince William Sound in Alaska in 1989. BP's well is spewing about 210,000 gallons of oil a day into the ocean, the Coast Guard estimates.

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