Oil leak threatens bird sanctuary

Tar balls thought to be the product of a relentless oil leak in the Gulf of Mexico have washed ashore on Dauphin Island, south of Mobile, Ala.

The entire island is a bird sanctuary. Several varieties of birds, including those heading to Canada on their annual spring migration, make the island their first landfall after arriving exhausted from Mexico's Yucatan Peninsula.

The thick blobs of tar, first spotted late Saturday, are the size of a dime to a golf ball. Cleanup workers have placed clusters of oil-absorbing synthetic fibres called pom-poms on the shore to trap the mess. And members of the U.S. Army National Guard have erected a fence of basket-like containers along the beaches.

Meanwhile, BP was trying to determine whether to try again to put a huge concrete box over the leak on the seabed.  

The oil company's first attempt to contain the oil failed Saturday when slushy ice-like crystals, formed by a mixture of gas and water, clogged the opening inside the top of the box, which is designed to funnel the oil to the surface.

BP moved the box 200 metres away after discovering the crystals. On Sunday, crews planned to secure the containment box 490 metres away from the leak site.

Warm water may be used to melt crystals

It had taken about two weeks to build the original dome and three days to cart it 80 kilometres out and slowly lower it to the well, 1.6 kilometres below the surface.

Options under consideration included raising the box high enough that warmer water would prevent the slush from forming, or using heated water or methanol.

BP was also considering putting a smaller containment dome over the leak site. It was debating whether it should cut the riser pipe undersea and use larger piping to bring the gushing oil to a drill ship on the surface.

Cutting the pipe is tough, and considered the less desirable option, chief operating officer Doug Suttles said.

The Deepwater Horizon rig exploded April 20, killing 11 workers. Oil started flowing from the leak two days later, at a rate of about 795,000 litres of crude a day.

As of Sunday, about 13.25 million litres had poured into the sea, or about a third of the 41.64 million litres spilled in the Exxon Valdez disaster.