Amoco Cadiz
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Summary
The Amoco Cadiz was a supertanker, owned by Amoco in the United States of America, that split in two, after running aground on Portsall Rocks, three miles off the coast of Brittany in March 16, 1978, resulting in the 5th largest oil spill in history.
En route from the Persian Gulf to Le Havre, France when it encountered stormy weather with gale conditions and high seas and a seemingly minor failure in the ship's steering gear started a slow drift to the French coastline.
The entire cargo of 1,619,048 barrels, spilled into the sea. A slick 18 miles wide and 80 miles long covered approximately 200 miles or 120 km of Brittany coastline. Beaches of 76 different Breton communities were oiled.
The isolated location of the grounding and rough seas restricted cleanup efforts for the two weeks following the incident. Severe weather resulted in the complete break up of the ship before any oil could be pumped out of the wreck.
As mandated in the "Polmar Plan", the French Navy was responsible for all offshore operations while the Civil Safety Service was responsible for shore cleanup activities. Although the total quantity of collected oil and water reached 100,000 tons, less than 20,000 tons of oil were recovered from this liquid after treatment in refining plants.
After long negotiations on financial terms betwenn the ship's captain and the master of a West German tug boat and two unsuccessful towing attempts, the towline finally broke during the argument and the ship drifted on the rocks.
Type of Oil
Both Arabian Light and Iranian Light crude oil are medium weight oils with an API gravity of 33.8. Bunker C is a heavy product with an API of between 7 and 14. A 12-mile long slick and heavy pools of oil were smeared onto 45 miles of the French shoreline by northwesterly winds.
Prevailing westerly winds during the following month spread the oil approximately 100 miles east along the coast. One week after the accident, oil had reached Cotes de Nord.
Oil penetrated the sand on several beaches to a depth of 20 inches. Sub-surface oil separated into two or three layers due to the extensive sand transfer that occurred on the beaches during rough weather. Piers and slips in the small harbors from Porspoder to Brehat Island were covered with oil.
Other impacted areas included the pink granite rock beaches of Tregastel and Perros-Guirrec, as well as the tourist beaches at Plougasnou. The total extent of oiling one month after the spill included approximately 200 miles of coastline.
Oil persisted for only a few weeks along the exposed rocky shores that experienced moderate to high wave action. In the areas sheltered from wave action, however, the oil persisted in the form of an asphalt crust for several years.
Environmental Impact
The nature of the oil and rough seas contributed to the rapid formation of a "chocolate mousse" emulsification of oil and water. This viscous emulsification greatly complicated the cleanup efforts. French authorities decided not to use dispersants in sensitive areas or the coastal fringe where water depth was less than 50 meters. Had dispersant been applied from the air in the vicinity of the spill source, the formation of mousse may have been prevented.
At the time, the Amoco Cadiz incident resulted in the largest loss of marine life ever recorded from an oil spill. Mortalities of most animals occurred over the two month period following the spill. Two weeks following the accident, millions of dead mollusks, sea urchins, and other bottom dwelling organisms washed ashore.
Diving birds constituted the majority of the nearly 20,000 dead birds that were recovered. The oyster mortality from the spill was estimated at 9,000 tons. Fishermen in the area caught fish with skin ulcerations and tumors.
Some of the fish caught in the area reportedly had a strong taste of petroleum. Although echinoderm and small crustacean populations almost completely disappeared, the populations of many species recovered within a year. Cleanup activities on rocky shores, such as pressure-washing, also caused habitat impacts.
The Amoco Cadiz spill was one of the most studied oil spills in history. Many studies remain in progress. This was the largest recorded spill in history and was the first spill in which estuarine tidal rivers were oiled. No follow-up mitigation existed to deal with asphalt formation and problems that resulted after the initial aggressive cleanup.
Additional erosion of beaches occurred in several places where no attempt was made to restore the gravel that was removed to lower the beach face. Many of the affected marshes, mudflats, and sandy beaches, were low-energy areas. Evidence of oiled beach sediments can still be seen in some of these sheltered areas. Layers of sub-surface oil still remain buried in many of the impacted beaches.
Legal Claims
In 1979, it was estimated to have caused $250 million in damage to fisheries and tourist amenities. The French government presented claims totalling $2 billion to United States courts.
See also
External links
- Oil Spills: A Case Study of the Amoco Cadiz Oil Spill :: Green Nature :: (http://greennature.com/article219.html) - Case Study of Amoco Cadiz oil spill
- Those were the days (http://www.westmidlands.com/days/1976-2000/1978.html) - Some information on March 18-24
- Amoco_Cadiz (http://www.le-cedre.fr/uk/spill/amoco/amoco.htm) - Information accompanied by text, including information on legal disputefr:Naufrage de l'Amoco Cadiz