In the days since a BP oil rig exploded and sank in the Gulf of Mexico, vast amounts of oil have been pouring into the water. The damage is worse than originally thought: the U.S. Coast Guard has revised its earlier estimate, indicating that some 5,000 barrels of oil are spilling into the water off the coast of Louisiana each day. As the slick moves toward the fragile coastline ecosystems, the race to contain it is underway. On Thursday, Homeland Security Secretary Janet Napolitano declared the spill “of national significance,” pledging to devote “every available asset” to stopping it.
In the meantime, BP is trying to contain it any way it can: in addition to using skimmers to remove the thickest substance, 76,000 tons of dispersant to break up the oil, and setting up miles of barriers to protect the coast, the company is experimenting with controlled burns—a last-ditch effort that carries environmental consequences. (Though burning oil changes its consistency, making less likely to coat marine life, according to the U.S. Coast Guard’s Rear Adm. Mary E. Landry, it creates a “black plume” of smoke.) Despite past experience with oil spills, there’s no tried-and-true way to contain them. Here’s a look at how the world’s top five marine oil spills were (or weren’t) contained:
5. ABT Summer: On May 28, 1991, there was an explosion aboard the ABT Summer, an oil tanker en route from Iran to Rotterdam. The ship, which was carrying 260,000 tons of oil, caught fire. After three days, it sank 1,300 km off the coast of Angola.* Because it was so far off-shore, there was no rush to clean up the damage; it was assumed that high seas would break up the large slick.
4. Nowruz Oil Field: On February 10, 1983, in the midst of the Iran-Iraq war, an oil tanker slammed into a platform at the Nowruz Oil Field in the Persian Gulf. The conflict delayed efforts to cap the ensuing spill, and an estimated 1,500 barrels drained into the water each day. In March, Iraqi planes attacked the platform, setting the oil slick ablaze. By the time the well was finally capped in September—an Iranian operation that killed 11 people—it had released some 260,000 tons of oil into the sea. The clean-up effort largely centered around the use of skimmers and pumps by Norpol, a Norwegian company.
3. Atlantic Empress/Aegean Captain: On July 19, 1979, two oil tankers, the Atlantic Empress and the Aegean Captain collided off the coast of Trinidad and Tobago during a tropical storm. The ships, which contained nearly 500,000 tons of crude oil between them, burst into flames on impact. Crews successfully extinguished the fire aboard the Aegean and it was towed to shore, but the blaze continued to rage on the Atlantic. After more than two weeks of firefighting efforts, an explosion sunk the ship, which had by then been dragged further out to sea. Dispersants were used to treat the spilled oil, curbing pollutants. In the end, an estimated 280,000 tons poured into the Caribbean—the record for a ship-source spill.
2. Ixtoc I: On June 3, 1979, Pemex, Mexico’s government-owned oil company, was drilling a 3.2 km deep oil well in the Gulf of Mexico, when the Ixtoc I exploded. The blow out, which occurred when the drill ran into high pressure, soon caught fire and caused the platform to collapse. A team of experts arrived quickly at the site, about 970 km south of Texas, but because of poor visibility and seafloor debris, it took divers until the following March to cap the well. In the meantime, between 10,000 and 30,000 barrels of oil poured into the water each day, totaling an estimated 454,000 tons. To slow the flow, mud (and later, steel balls) were dropped into the well. According to Pemex, half the oil burned when it reached the surface, and a third evaporated. Norwegian experts contained the spill using skimming equipment and booms.
1. Gulf War: In the first days of the Gulf War, Iraqi military forces opened the valves at the Sea Island oil terminal in Kuwait, releasing vast amounts of crude oil into the Persian Gulf. The spill, which began on January 21, consisted of up to eight million barrels (between 1,360,000 and 1,500,000 tons), making it the largest in history. Because of the war, clean-up was delayed, but an international effort did eventually get underway. Using smart bombs, Coalition forces were able to seal the open pipelines at the Al Ahmadi facility, and American and Dutch workers built ponds in the desert to store the oil they pumped from the water. Booms and skimmers were used to keep the oil away from the desalination plants, which provided drinking water to residents in the area. In the end, the spill was not as catastrophic as initially feared: roughly half the oil evaporated, two to three million barrels washed ashore and a million barrels were recovered.
(*Corrected from an earlier version, which erroneously stated that the ABT Summer sank 130,000 km off the coast of Angola.)