FAQ: General Questions About Oil Spills

Q. I'm doing a report on oil spills. Do you have any information about oil spills that might help me?

A. There's a lot of information about oil spills on this Web site and on our IncidentNews Web site. We've made a list of some of the things you can find.

Q. In the U.S., what precautions have been taken to reduce the likelihood of oil spills?

A. Regulations and laws enacted in the United States during the past 10 years or so have greatly improved prevention of oil spills. These have included safety regulations, requirements for construction of new oil tankers (such as requirements for double hulls), procedures for responding quickly when ships run aground so they can be refloated without spilling oil, and more rigorous inspection requirements. Of these laws, the most important is the Oil Pollution Act of 1990, passed by Congress after the Exxon Valdez oil spill.

Not all oil spill prevention focuses on technology issues. Human factors play a very important role in spill prevention. You can find out more information about this topic at these U.S. Coast Guard Web sites: the Prevention page, the Prevention Through People (PTP) program, and the U.S. Coast Guard Marine Safety, Security and Environmental Protection Web page.

Q. What exactly is an oil spill?

A. The kind of oil spill we usually think about is the accidental or intentional release of petroleum products into the environment as result of human activity (drilling, manufacturing, storing, transporting, waste management). Examples would be things like well blowouts, pipeline breaks, ship collisions or groundings, overfilling of gas tanks and bilge pumping from ships, leaking underground storage tanks, and oil-contaminated water runoff from streets and parking lots during rain storms.

Apart from oil spills caused by human actions, oil also is released into the environment from natural oil seeps in the ocean bottom. One of the best-known areas where this happens is Coal Oil Point along the California Coast near Santa Barbara. An estimated 2,000 to 3,000 gallons of crude oil is released naturally from the ocean bottom every day just a few miles offshore from this beach. The photo at right shows a large patty of weathered oil on the beach at Coal Oil Point.

Q. When an oil spill happens, does the oil spread quickly or slowly?

A. When an oil spill happens, it spreads very rapidly unless it is contained by something (like a boom or a boat slip in a harbor). The lighter (less dense) the oil, the faster it spreads out to form a very thin sheen. For example, gasoline spreads faster than a heavy black oil, such as #6 fuel oil. Faster currents and winds can make oil spread faster. Temperature can sometimes make a difference in how fast an oil spreads. Colder oil is more viscous (doesn't flow as well) and spreads more slowly. If it gets cold enough, oil doesn't flow like a fluid anymore, but acts more like a solid (like tar or silly putty). We have to remember that when responding to oil spills in arctic areas. But under most conditions, within a very short period of time (minutes to a few hours for large spills), even very heavy oil has usually spread out enough that it is about as thin as a coat of paint on the wall.

You can test how oils spread with our Oil Floats and Spreads experiment. When you do this experiment, try using different kinds of oil, such as salad oil and baby oil (which is thinner, or "less viscous," than salad oil, so it spreads faster). You also might want to try using molasses to simulate heavy fuel oils (molasses is thicker, or "more viscous," than salad oil, so it spreads more slowly).

Q. I'm researching oil spills in rivers. I have heard that there is a different way of cleaning up river spills. Have you any information on this subject?

A. Oil spills on rivers can indeed behave differently than spills in the open ocean or in bays. Visit our Oil Spills in Rivers Web page to learn why.

Q. I know that oil spills into the water from small, everyday sources, like cars, not just from major oil spills. Wouldn't more oil leak into the water from all these sources, taken together, than from even the biggest oil spills (like the Exxon Valdez)?

A. Yes. Researchers from NASA and the Smithsonian Institution have estimated the amounts of oil that spill from small and large sources. The graph on their Oil Pollution page shows that much more oil spills into the water from small sources than from major tanker accidents. In Threats to the Health of the Oceans, they also estimate that just 5% of the oil that spills into the ocean comes from major oil spills. A recent report from the National Academies of Sciences, Oil in the Sea, similarly finds that "nearly 85 percent of the 29 million gallons of petroleum that enter North American ocean waters each year as a result of human activities comes from land-based runoff, polluted rivers, airplanes, and small watercraft." 

Also, as you can see from the state of Alaska's FY 05 Response Summaries, most accidental oil spills are much smaller than the major disasters, like the Exxon Valdez spill, that you hear about on the news.

Finally, toxic chemicals as well as oil affect the quality of our water. The U.S. EPA offers a set of fact sheets, Nonpoint Source Pointers, explaining "nonpoint source pollution" (water pollution caused by sources other than big accidents).

Q. Can you tell me where I can obtain information in French on oil spills?

A. Yes, we can. Here are some French-language Web sites on oil spills:

• Les hydrocarbures, l'eau et le mousse au chocolat An explanation of oil spills and their effects, along with some ideas for experiments, from Environment Canada.
  
• Cedre (Le Centre de Documentation, de Recherche et d'Expérimentations sur les pollutions accidentelles des eaux), in Brest, France. Cedre's staff members are primarily researchers, but they offer some materials for the interested general public, such as an archive of oil spill-related questions and answers, and information about significant oil spills that happened in Europe.
  
• Pollutions Maritimes: Erika, Prestige et les autres A Web site on recent French oil spills, developed by students. Includes a link to ask scientists your questions about oil spills, along with an archive of past questions and answers.
  
• Erika: Le dossier de la marée noire A special section of the Ouest-France newspaper on the December 1999 oil spill from the freighter Erika, off Britanny.

Q. Does spilled oil affect the salt in seawater?

A. That's a new question for us! As spill responders, we're usually concerned about how salt in the water affects oil, not vice-versa. Water salinity is a very important determinant of how oil physically behaves once it is released, because it influences whether the oil floats or sinks (oil floats more readily in salt water). It also affects the effectiveness of some of the chemicals that might be used to treat a slick (like chemical dispersants). For these reasons, water salinity is one of the physical parameters our oceanographers and computer modelers take into account as we gather information during a spill response.

Until recently, no one much cared how oil affected salt. But the question became a big concern in December 1999 when the freighter Erika released a large amount of oil off the coast of Britanny, France. As you might know, a gourmet sea salt, called Sel de Guerande, is produced in salt marshes along the coast of Britanny. There was great concern that the spilled oil, if it were to enter the salt marshes would taint the flavor of this famous product. Sea salt production was therefore temporarily halted as a precaution. This is the only time we can think of when the effects of oil on salt became an issue!

Q. How long does it take for spilled oil to seep into the ground?

A. The way oil behaves depends on the kind of oil, the kind of ground it has spilled onto (e.g., coarse or fine sand, rock, mudflat, and so on), the kind of environment it spills into, and the weather at the time of the spill. See our Web page, Oil Types, to learn about the different types of oil. For example, while a light oil will penetrate quickly into a coarse sediment, a heavy oil will penetrate more slowly or not at all. Oil may not penetrate at all into a fine-grained beach, because the sand grains are so closely packed together that there's little space between them for the oil to penetrate. In hot weather, oil is more likely to seep into the ground than in cold weather, because oil doesn't flow as easily when it's cold.