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Bioremediation

Exxon Valdez

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Exxon Valdez
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Oil Transfer
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The remaining oil on the Exxon Valdez being transfered to the Exxon Baton Rouge, another oil tanker

 
     Just after midnight on March 24, 1989, the Exxon Valdez oil tanker ran aground on Blight's Reef in Prince William Sound, Alaska.  Oil began to leak from the vessel and into the water.  By the time it was over, 37,000 tonnes of oil had been spilled.  This figure represents only about 20% of the total amount of oil that the ship had been carrying.  The other 80% was transferred to another tanker shortly after the grounding to prevent it from leaking into the water as well.  The spilled oil affected 1,300 miles of coastline. 
 
     Although the Exxon Valdez oil spill was the largest in U.S. history, it is not among the largest in the world.  In fact, the Exxon Valdez spill is currently ranked # 53 on the list of the world's largest oil spills.  See the oil spill charts for a clearer picture of how the Exxon Valdez spill compares with other spills. 
 
     The reason that this spill was given so much media attention is that it happened so close to the coastline.  This resulted in large quantities of oil washing up on the beaches.  Prince William Sound is known as a pristine environment.  It is for the most part untouched by man. This makes it very appealing to many species of wildlife.  The oil have a devastating affect on the animals in the area.  After the spill 35,000 seabird carcasses and 1,000 sea otter carcasses were found.  These figures, however, do not give an accurate death toll because most of the carcasses would have sunk.  Estimations put the death toll at 250,000 seabirds, 2,800 sea otters, 300 harbour seals, 250 bald eagles, as many as 22 killer whales, and billions of salmon and herring eggs.  Some of the species have been able to recover from this devastation, some are showing signs of improvement, but there are 8 species that have shown no signs of improvement since the spill occurred 15 years ago. 
 

An Oil Covered Sea Otter
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An Oil Covered Duck
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Click on either picture to see how the animals are recovering from the spill.

     The Exxon Valdez oil spill was the first time that bioremediation was used on a large scale.  Many of the beaches that were only lightly coated in oil were treated with bioremediation.  Some heavily and moderately contaminated areas were also treated with bioremediation.  However, they required an initial physical treatment.  In situ bioremediation was used.  The main factor affecting that decision was the location of the spill.  Also, the microorganisms already present on the beaches were capable of degrading the oil.  The beaches were sprayed with fertilizers to provide an excess of nitrogen and phosphorus to the microorganisms so that they could grow and more readily.
 
     Almost all of the remaining beaches were treated with high pressure, hot water treatment.  This involved people standing on the beach and spraying boiling water with a firehose.  The water would carry the oil back into the ocean.  Here it was collected using booms to gather it up and then sucked up.  The cleaup efforts involved a massive number of people and equipment.  At the peak of the cleanup efforts, there were over 10,000 workers, 1,000 boats, and 100 airplanes involved.  Despite those numbers, to this day not all of the beaches have been cleaned.  The cleanup efforts were called off after the fourth summer.  Altogether, $2.1 billion was spent on the cleanup. 

Spraying
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Beaches were sprayed with high pressure hot water to wash the oil back into the ocean for collection

Oil Remnants
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Surveying done in 2001 revealed a lot of oil remaining in the area

Click here to view a slide show about the Exxon Valdez oil spill.