Gulf oil spill: Louisiana's berm plan bold but full of uncertainty

China's Ming Dynasty built the Great Wall to thwart invasion. The French built their Maginot Line. Now Louisiana is gearing up to build offshore embankments of sand as bulwarks against the Gulf oil spill.

The embankments, or berms, will be placed on the seaward side of several of the state's fragile and vanishing barriers islands, and in some cases form temporary barrier islands, in order to reduce the amount of crude oil invading coastal marshes.

Since the drill-rig blowout April 20, which killed 11 rig workers and destroyed the Deepwater Horizon platform, the well has been spewing between 12,000 and 19,000 barrels a day into the Gulf, according to federal estimates. Scientists outside the government have independently estimated flows several times the officials figure.

IN PICTURES: Gulf oil spill's impact on nature

Late last week, BP installed a containment cap on the wellhead that appears to be capturing about 10,000 barrels a day and sending it to a ship at the surface. But oil is expected to continue leaking from blowout – although at reduced amounts – until BP finishes its two relief wells and can use them to choke the flow.

Oil has expanded its patchy landfall from the western edge of the Mississippi River Delta to beaches along Mississippi, Alabama, and the Florida Panhandle.

During a briefing at the White House today, US Coast Guard Adm. Thad Allen told reporters that he expected the cleanup of oil on the sea surface to continue into the fall, assuming BP's two relief wells are finished in August. But, he added, the amount of time for dealing with "long-term issues of restoring the environment and the habitats and stuff will be years," with oil-fouled wetlands a critical concern.

The berm plan

The berm plan, which President Obama approved last week, initially involves building about 35 miles of berms in six segments – the longest of which, off the Chandeleur Islands east of the Mississippi Delta, stretches 13 miles. In 2005, Hurricane Katrina walloped the string of islands some 50 miles long, turning them into shoals.

The initial berm segments are part of an overall 90-mile effort that the state of Louisiana estimates would cost $350 million to build over a six-to-nine-month period.

The use of berms "has some sound concepts behind it," says Denise Reed, who currently heads the Pontchartrain Institute for Environmental Sciences at the University of New Orleans.

First, she says, it's easier to clean up oil when it's on a sandy beach than it is to remove it from tidal wetlands. Second, well-defined channels between these temporary artificial barrier islands can serve to focus incoming oil in ways that could make it easier to corral with booms and skim.

"One of the reasons it's so easy for the oil to get into the wetlands in Louisiana is that the barrier shoreline is so degraded," Dr. Reed explains.

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