Can an oil spill really be cleaned up?

Since the Gulf oil spill of April 2010, people have been asking us, “Can you really clean up an oil spill?”

Nancy Rabalais: Well, not entirely. The oil will penetrate into habitats that it’s difficult to get the oil out of.

That answer comes from biological oceanographer Nancy Rabalais of the Louisiana Universities Marine Consortium.

Nancy Rabalais: Eventually, oil does degrade. The toxic fractions are removed through natural processes, oxidation and photodegradation and things like that, microbial decomposition. It’s just that it’s not something that’s going to go away overnight, for sure, or even in a couple of years.

She said the April 2010 explosion that sent millions of gallons of crude oil gushing into the Gulf of Mexico threaten the hard-to-reach salt marshes lining Louisiana’s coast.

Nancy Rabalais: You can’t just get to them by boat. You can’t get to them by land. Helicopter, I guess you could. There’s just too much marshland involved. So there will be some oiling that can’t be easily removed without doing further damage to the marsh.

Dr. Rabalais compared the 2010 Gulf oil spill to one in 1979, called the Ixtoc oil spill, which coated some Texas beaches with oil.

Nancy Rabalais: I was involved in the clean up of an oil spill in Texas and a salt marsh similar to the Mississippi River, and there were places where you could get in and clip grass, put the oil off, and use absorbent pads to get the oil off. But you have to be careful of how much of that you do, because you can damage the marsh. There were areas that were burned that removed the oil, but there was some long-term permanent damage of the marshes in that area. And then there were other areas that were heavily oiled that got no remediation and those marshes died back for a couple of years. It took a while for them to recover.

Dr. Rabalais spoke about what the recovery might be like from the Gulf oil spill of 2010.

Nancy Rabalais: It always depends on what type of habitat and how long it’s exposed to that oil and the form that the oil comes in. The Ixtoc oil well explosion in the Southern Gulf of Mexico that came ashore in Texas is a good example of a long-term spill that went many, many, many thousands of miles away and hit sandy beaches. Sandy beaches are a little easier to clean, because you can scrape the oil off. But in this particular instance there were ‘tar reefs’ that built up offshore. Oil got into the animal burrows, so that any time you had an erosion event, which is typical on a sandy beach, you got more oil exposed. That goes on for many years, regardless of how much you try to scrape off the surface of the sand. The salt marshes are similar.

The recovery, said Rabalais, could take many years for places where removal is difficult, or not possible, because the oil is going to keep seeping out of the sediments.

Nancy Rabalais: So it’s a long term process, especially depending on the type of habitat and how much more oil we expect to come out. That’s a big question. The Ixtoc well went uncapped for about nine months, so it lost about 173 million gallons of oil. Right now, with the estimates that we’re getting for the Deepwater Horizon is about 210,000 gallons a day. I’ve done the calculations as of today, and we should have about two million gallons out there. If it takes about 90 days to get it under control, then we’re looking at the 200 million gallon limit, which is over the size of Ixtoc in its nine months of being uncapped.

Rabalais contrasted cleanup of the Gulf oil spill with that of the Exonn-Valdez spill off Alaska in 1989.

Nancy Rabalais: They’re two very different oil spills. The Exxon-Valdez lost about ten or eleven million gallons of oil, and we’re getting close to exceeding that pretty soon in the Gulf. It was in a narrow inlet. It all came out at once. It was a harsh environment, but it was pretty much contained to one area, again, with very sensitive critical habitat for fish and sea birds and things like that. There was a very aggressive clean-up there, a lot of washing of the rocks, detergent, dispersents, but it’s the same sort of situation as the Ixtoc oil spill on the Texas beaches. It seeps into the cobbles and keeps coming out for many years, ten years or more probably. So this one, it’s coming out from 5,000 feet down. It’s coming out as a huge surface slick, over many square miles of area, and it’s not contained within a narrow area where you think you can boom it off and recollect the oil.

May 5, 2010

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