Over two decades after the devastating Exxon Valdez oil spill off the coast of Alaska, significant quantities of oil can still be found covering the state's shores and beneath gravel beaches, a new study has discovered.
Over 21,000 gallons of crude oil remains of the 11 million gallons of crude oil that gushed from the stranded tanker Exxon Valdez on the night of 23 March 1989. Traces of Valdez's oil have been detected as far as 724km away from the spill-site in Prince William Sound, and the toxic film that coats Alaska's shores remain a danger to wildlife, entire eco-systems and the lives of local people.
Writing in Nature Geoscience, a team of scientists found that oil just a few inches down was dissipating up to 1000 times slower than oil on the surface.
Despite Valdez not being up there with the largest oil spills of all time, it is one of the most high-profile and considered to be one of the worst environmental disasters of its kind, covering more than 2000km of coastline and killing thousands upon thousands of seabirds,fish and other water-dwelling creatures.
Noted: One tonne = approx. 308 US gallons
1. Gulf War oil spill - 1,500,000 tonnes
The Gulf War oil spill is regarded as the worst oil spill in history, resulting from actions taken during the Gulf War in 1991 by the Iraq military.
It caused considerable damage to wildlife in the Persian Gulf especially in areas surrounding Kuwait and Iraq. Estimates on the volume spilled range from 42 to 462 million gallons; the slick reached a maximum size of 101 by 42 miles and was 5 inches thick. Despite the uncertainty surrounding the size of the spill, figures place it 5 to 27 times the size (in gallons spilled) of the Exxon Valdez oil spill, and more than twice the size of the 1979 Ixtoc I blow-out in the Gulf of Mexico.
According to a study sponsored by UNESCO, Bahrain, Iran, Iraq, Kuwait, Oman, Qatar, Saudi Arabia, the United Arab Emirates and the United States, the spill did little long-term damage. About half the oil evaporated, a million barrels were recovered and 2 million to 3 million barrels washed ashore, mainly in Saudi Arabia.
On January 21, 1991, Iraqi forces opened valves at the Sea Island oil terminal and dumped oil from several tankers into the Persian Gulf. The apparent strategic goal was to foil a potential landing by U.S. Marines. The oil moved southward, ending up on the north coast of Saudi Arabia, endangering the fragile intertidal zones and mangrove forests and destroying wildlife habitats.
2. Ixtoc I oil well – 480,000 tonnes
Ixtoc I was an exploratory oil well in the Gulf of Mexico, about 600 miles (970 km) south of the U.S. state of Texas. On June 3, 1979, the well suffered a blowout and is recognized as the second largest oil spill in history.
Mexico's government-owned oil company Pemex (Petróleos Mexicanos) was drilling a 2-mile (3.2 km) deep oil well, when the drilling rig lost drilling mud circulation. In modern rotary drilling, mud is circulated down the drill pipe and back up the casing to the surface. The goal is to equalize the pressure through the shaft and to monitor the returning mud for gas. Without the circulating mud, the drill ran into high pressure gas which blew out the oil (known as a blowout). The oil caught fire and the platform collapsed.
In the next few months, experts were brought in to contain and cap the oil well. Approximately 10 thousand to 30 thousand barrels per day were discharged into the Gulf until it was finally capped on March 23, 1980. Prevailing currents carried the oil towards the Texas coastline. The US government had two months to prepare booms to protect major inlets. Mexico rejected US requests to be compensated for cleanup costs.
3. Atlantic Empress / Aegean Captain – 287,000 tonnes
The Atlantic Empress was a Greek oil tanker that was involved in two large oil spills. The spills together are the fourth largest total oil spill on record and the largest ship-based spill.
On July 19, 1979, during a tropical rainstorm, the ship collided with the Aegean Captain, off Trinidad and Tobago, spilling 287,000 metric tonnes of oil consigned to Mobil. The damage incurred from the collision was never completely remedied, and while being towed on August 2, the Atlantic Empress continued to spill an additional 41 million gallons (all together being 276,000 tonnes of crude oil) off Barbados. The Aegean Captain also spilled a large quantity of oil from her No. 1 tank. The Atlantic Empress sank on 3 August in deep water and her remaining cargo solidified. The spill from the two ships fortunately never came ashore.
4. Fergana Valley – 285,000 tonnes
Date: March 2, 1992
88 million gallons of oil spilled from an oil well. (No more information)
5. Nowruz oil field – 260,000 tones
In 1983, the Nowruz Oil Field in the Persian Gulf, Iran, was involved in a number of oil pollution incidents. On February 10, 1983, a tanker collided with a platform. The platform developed a 45-degree tilt and had to be shut down. Wave action and corrosion apparently caused the riser to collapse into the wellhead causing a spill of approximately 1,500 barrels per day. The well was not capped because the field was in the middle of the Iran/Iraq war zone. This platform was attacked by Iraqi planes in March and the resulting slick caught fire.
This well was capped by the Iranians on September 18, 1983. Eleven people were killed during the operation. In March 1983, a nearby platform was attacked with rockets by Iraqi helicopters. The platform burned and spilled oil at an initial rate of approximately 5,000 barrels per day. The rate slowed to about 1,500 barrels per day in the two years before the well was capped. In May 1985, the fire was extinguished and the well was plugged with the assistance of divers. Nine men died during these operations. Approximately 733,000 barrels of oil spilled into the sea as a result of this incident. It is estimated that the rate of oil leaking into the Persian Gulf in mid-May of 1983 was between 4,000 and 10,000 barrels per day due to more war-related activity or the collapse of burning platforms. As a result of this incident, a cooperative program for large-scale trajectory modeling was developed between the National Oceanic and Atmospheric Administration and Kuwait's Environment Protection Council under the Ministry of Public Health.
Sources: wikipedia.org, IncidentNews.gov, ngoilgas.com