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Amoco Cadiz SpillAmoco Cadiz SpillBrittany, France 03/16/78 Incident Summary On March 16, 1978, the Amoco Cadiz ran aground on Portsall Rocks, three miles off the coast of Brittany due to failure of the steering mechanism. The vessel had been en route from the Arabian Gulf to Le Havre, France when it encountered stormy weather which contributed to the grounding. The entire cargo of 1,619,048 barrels, spilled into the sea. A slick 18 miles wide and 80 miles long polluted approximately 200 miles 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. Behavior 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. Countermeasures and Mitigation A 2.5 mile long segment of boom protected the Bay of Morlaix. Although it required constant monitoring, the boom functioned properly because this sheltered area was protected from severe weather and from receiving excessive quantities of oil. Boom was largely ineffective in other areas due to strong currents and enormous quantities of oil. Skimmers were used in harbors and other protected areas. However, skimmer efficiency was limited due to the blocking of pumps and hoses by seaweed. Vacuum trucks were used to remove oil from pier and boat slip areas where the seaweed was thick. "Honey wagons", vacuum tanks designed to handle liquid manure, were effective in pumping out the emulsified oil along the coast. These wagons were able to pump oil, water, and seaweed. After the water and oil were separated as much as possible, the tanks were emptied through filter-buckets into interim storage tanks. When interim storage tanks were not available, the oil mixture was stored in large holes that were dug in the ground and lined with plastic sheets. Stranded oily seaweed was manually removed from the beaches using rakes and front-end loaders. Natural cleaning of the sand by wave action occurred on oil penetrated beaches after ploughing and harrowing of the sediments. Both artificial fertilizers and bacterial cultures were poured on the oily sand before harrowing. Several brands of diluted and concentrated dispersants, including BP 1100 X, Finasol OSR, BP 1100 WD, and Finasol OSR -5, were used by the French Navy. Good dispersion of oil was difficult since the emulsified oil was several centimeters thick in some places. Approximately 650 metric tons of oleophilic chalk, Nautex, was applied in an effort to sink the oil and prevent it from entering the "goulet de Brest." After one month at sea, the oil was so viscous that the chalk could not penetrate it. A rubber powder made from old tires was applied to promote oil absorption. The powder was spread with water hoses aboard French Navy ships or applied manually by workers from small fishing boats. Wave action proved to be insufficient in mixing the powder with the oil. The powder had little effect on the slick because it remained on top of the oil. High-pressure hot water (fresh water at 2,000 psi, heated to 80° - 140°C) was very effective in cleaning oil from rocky shoreline areas during the third and fourth months of cleanup. A small amount of dispersant was applied to prevent the oiling of the cleaned rocks during the next high tide. Several of the impacted rivers contained oyster beds and marshes that required manual cleaning. Soft mud river banks were cleaned by using a low pressure water wash to push the oil down the river. To make collection more efficient, a sorbent material was mixed with water and poured in front of the washing nozzles. The oil was later collected by a locally developed device called an "Egmolap." This device was able to collect any material floating in sheltered areas. Much of the collected oil was stored at Brest and Tregastel and treated with quick-lime for encapsulation and stabilization. Other Special Interest Issues 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. Fishes with skin ulcerations and tumors were caught by fishermen in the area. 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. Addition 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. References This content has been excerped from: Oil Spill Case Histories 1967-1991: Summaries of Significant U.S. and International Spills |
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