Oil Spill Fallout: 'You Can't Pressure-Wash a Marsh'

(May 21) -- Louisiana Gov. Bobby Jindal has been arguing ever since the Deepwater Horizon oil rig blew up a month ago that the best way to protect his state's delicate coastal wetlands is to wall the oil out. His plan is to dredge the Gulf of Mexico and construct temporary islands to protect the marshes. It can seem like an attempt to defy the tide with sandcastles.

But as the gulf oil spill reached the wetlands this week, its toxic slick brought a new perspective on his proposal. For all the effort required to shield the marshes with emergency dredging, it could well be a better course than waiting and having to remove the oil afterward.

Salt-water marshes rank as the most environmentally sensitive places on Earth to clean up after a spill, according to a scale devised by the National Oceanographic and Atmospheric Administration. Louisiana's marshes are especially vulnerable as they serve as nursery to virtually all the fish, birds and wildlife that inhabit the gulf -- and it is now nesting season. So cleanup crews will have to tread a fine line between helping the marshes recover and hastening their demise; mop-up techniques that may work fine on the sandy beaches of Mississippi, Alabama or Florida could be fatal to a wetland.

"Remember the photos of the workers pressure-washing the oil off boulders in Alaska? You can't pressure-wash a marsh," says Denise Reed, interim director of the University of New Orleans' Pontchartrain Institute for Environmental Studies.

She warns that restoring Louisiana's marshes, which wind through 7,700 miles of shallow estuaries, inlets, bays, reefs, and passes, will be "very, very complicated."

Irving Mendelssohn, a Louisiana State University botanist who specializes in wetland plants, said the primary danger to the marshes from this spill is that the plants, which hold the soil together, will suffocate from multiple coatings of oil.

"Once they're dead, the soil collapses," he said. "Then the soil becomes flooded and can't grow back. The low areas that were marshes become ponds, the ponds form lakes and then the wetland disappears."

Complicating matters further, even cleanup techniques that work in certain marsh areas will not work in others. Hurricane Katrina caused nearly 50 oil spills in Louisiana. John Pine, a former Louisiana State University scientist who cataloged the effort, said each required a "drastically different" approach.

For Every Method, a Limitation

Scientists cleaning up the marshes from the Deepwater Horizon spill will likely draw from these commonly used strategies:

• Burning oil-coated plants, which removes oil quickly and minimizes trampling.
• Low-pressure flushing, which helps push oil into areas where it can be vacuumed up or absorbed.
• Cutting back vegetation to leave plants intact and prevent oiling of birds.
• Adding nutrients to speed natural degradation of the oil.
• Doing nothing. Oil that degrades over time hardens into a crust similar to asphalt, and letting Mother Nature take her course has the advantage of causing no collateral damage.

But each of these methods has limitations, some of them serious.

Cutting plants back, for example, only works in small areas -- and there may not be many of those with a spill that has pumped more than 4 million gallons of oil into the Gulf since April 20.

Introducing nutrients to accelerate the activity of natural microbes in the marsh that "eat" oil has limited potential, since oxygen levels in wetland soils are often so low that microbe activity is limited whether nourishment is added or not.

Likewise, low-pressure flushing only works when oil is floating on the surface.

"From an air boat, you can herd the oil to some central collection point where absorbents or vacuums can pick it up," Mendelssohn said. "If the oil is already on the marsh grass, using low pressure would erode the soil."

Burning is considered one of the most effective techniques. It was successfully used to clean up several of the Katrina-caused spills, and in one instance, new shoots appeared on plants within two or three days, Mendelssohn said. But there are limits to how and when burning can be used. Marshes with low water levels can't be burned without killing the plant roots.

The path of the oil from the Deepwater Horizon spill, which is washing ashore at the outer fringe of the marsh near the mouth of the Mississippi River along the long stretch of coastline known as the bird's foot delta, presents yet another wrinkle.

"I'm not too keen on burning grass at the boundary of marsh and open water," said Ed Overton, a retired Louisiana State University professor of environmental science. "If you burn to the front of the coastline, you're killing that and then we'll have further erosion."

When oil has been in the water for a length of time, the flammable toxins will have already evaporated, said Wes Tunnell, associate director of the Harte Research Institute for the Gulf of Mexico at Texas A&M University at Corpus Christi.

"Burning typically doesn't work once the oil has been on the surface for a while," he said. "You can put a match on it and it won't burn."

The Lessons of Ixtoc1

Tunnell was a young marine biologist in 1979 when the Ixtoc1 oil rig exploded in the Bay of Campeche off the coast of Mexico in about 200 feet of water. During the nine months that it took to shut down the well, 140 million gallons leaked into the gulf, creating what still ranks as one of the worst accidental oil spills in history.

Two months after the leak began, the oil arrived on Texas beaches and eventually left a strip of oil, 30 feet wide in places, that stretched north for 150 miles. What scientists did next may provide a lesson for Tunnell's neighbors up the coast.

"We let it hit the beaches," he said. "That's only a three on the sensitivity scale. But we had to stop it at all costs from coming into bays and estuaries, which rank a ten. We boomed off three inlets on the south Texas coast with triple and quadruple booms. We stopped about 90 percent of it."

In Louisiana, Jindal wants to mound up sand in several areas to keep the oil from moving inland. As of late this week, oil has washed up along 34.5 miles of coast, said Chris Macaluso, a spokesman for Jindal's coastal activities office. But the potential impact area stretches over two-thirds of the state's entire coast, he said.

As heavy oil moved into the marshes at Pass a Loutre, where the Mississippi's mouth meets open water, Jindal stepped up his campaign to persuade the Army Corps of Engineers to grant emergency permits so the dredging can begin and sand booms can go up along the Chandeleur Islands and across the bottom of Barataria Bay and Timbalier Bay. Jindal estimates the work would take 10 days to complete once dredging begins. The project has a $350 million pricetag, which Jindal has said he wants BP to pay.

Environmentalists have lent cautious support. As with all efforts to combat the Deepwater Horizon spill, it seems, there are downsides to the dredging plan as well.

Karla Raettig, director of the National Wildlife Foundation's coastal restoration program, notes there isn't much sand to dredge in the area. "They need to be careful where they take the sand," she said. "And the barriers will become contaminated. But this is a lesser of two evils."