Oil Spill Consequences
Oil being skimmed from the sea surface in Prince William Sound, AK.
Engineering Connection
When oil spills occur, environmental engineers help clean them up. They determine which type of cleanup method is best for different situations by examining the weather patterns of the area, the type of oil spilled, and what living creatures and natural environments are being affected by the spill. Their efforts, plus those of many rescue workers, help restore habitat after such a disaster occurs.
Introduction
The Exxon Valdez oil spill was one of the largest oil spills in history. It took place in Alaska in March 1989 when an oil tanker ran aground, spilling 10.8 million gallons of crude oil into Prince William Sound. While this was a huge spill, it was only a small fraction of what the U.S. uses in oil in any one day. The U.S. uses about 700 million gallons of oil every day. That is a lot of oil—enough to completely fill nine school gymnasiums!
How do we use oil?
Often, oil spills are caused by human mistakes. Sometimes, they happen during natural weather disasters, such as when a hurricane destroys oil mining equipment or oil tankers; other times, they occur when large industry machinery breaks down. Unfortunately, spills are sometimes caused by deliberate acts, such as citizens dumping oil illegally or even during times of conflict (war) as a means of sabotage.
Several oil characteristics make oil spills very dangerous and difficult to clean up. One important quality of oil is that it is less dense then water, which means it floats in water. When an oil spill occurs, environmental engineers work to help clean it up.
Have you ever noticed a rainbow puddle on the street or parking lot after a rain? That rainbow sheen that you see on top of the water is oil from vehicles that has leaked onto the ground. Environmental engineers are responsible for assessing what type of cleanup method is best for different situations. They examine the weather patterns of the area, the type of oil that was spilled, and what living creatures are, or will be, affected by the spill. They consider the nearby community and the population of plants or animals in the area.
Some of the methods engineers use are dispersants (chemicals used to break down the oil); booms and skimmers (used to contain the oil and avoid spreading); absorbents and vacuum cleaners; burning the oil; and biodegradation (the use of microorganisms that digest oil). Today, we are going to act as if we are environmental engineers and learn how these different techniques can be used to clean up oil spills.
Exxon Valdez: What happened?
At 9:12 PM on March 23, 1989, the Exxon Valdez departed from Prince William Sound, Alaska, with several people in charge of the ship. The pilot, captain and the helmsmen all were responsible to steer the 986-foot ship—carrying 53,094,510 gallons of oil—through the Valdez Narrows. Navigating through the Valdez Narrows is exceptionally challenging because of the Bligh Reef, which makes the narrows just 500-feet wide.
That night, the Exxon Valdez came across icebergs, so the captain ordered the helmsmen to turn the ship out of the shipping lanes and around the icebergs. Later that evening the wheelhouse was turned over to the third mate and a different helmsman. They were given specific instructions to turn the ship back into the shipping lanes at a certain point to avoid the reef. However, due to reasons unknown, the helmsmen did not steer the vessel back to the channel, and at 12:04 AM on March 24, the Exxon Valdez ran aground on Bligh Reef, spilling 10.8 million gallons of oil into Prince William Sound.
It was unclear who was at fault, but was likely some type of human error. Later investigations charged the captain with negligent discharge of oil. He was ordered to pay a $50,000 fine and give 1000 hours of community service. The Exxon Shipping Company continued operations under a new name, Sea River Shipping Company. The Exxon Valdez was repaired and renamed the Sea River Mediterranean, and prohibited from entering Prince William Sound. In 2012, the ship was sold for scrap metal in India.
Effects of the Spill
It is estimated that 10.8 million gallons of oil leaked from the Exxon Valdez—enough oil to fill 125 Olympic-sized swimming pools. The spill is the largest ever in the U.S. Oil covered about 1,300 miles of shoreline, with 200 miles heavily covered and 1,100 lightly covered. The impact of an oil spill of this magnitude is tremendous. Exxon paid $2.1 billion to clean up the spill, but the effects are still being felt today. The ecological impacts are impossible to know because the effects last a long time. It is estimated, however, that the oil spill killed 250,000 seabirds, 2,800 sea otters, 300 harbor seals, 250 bald eagles 22 killer whales and billions of salmon and herring eggs. Ten years later, only two of the 23 species injured by the spill have recovered.
Cleanup
During cleanup of the Exxon Valdez oil spill, environmental engineers developed methods that could prove helpful in similar large disasters. They tried traditional mechanical methods: backhoes to sift through sand covered with oil-soaked soil and high pressure hot and cold water treatments to wash the oil off the shore to be scooped up by skimmers or adsorbed by adsorbent material. Additionally, they used the uncommon method of bioremediation: adding fertilizer to the beaches to promote the growth of bacteria that can degrade the oil. During the Exxon Valdez oil spill clean up, environmental engineers learned a lot and optimized many processes. The use of bioremediation, for example, was not commonly used before this oil spill, and now is used for many different applications. Conversely, the use of hot water treatment was very common before this oil spill. However, during the Valdez cleanup, they found that hot water did more damage then good, because it harms the small water organisms.
