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An overview of oil spills, their impact on aquatic environments, and the methods used to prevent, contain, and clean up oil spills. It covers topics such as the behavior and effects of oil spills, mechanical containment and recovery, alternative countermeasures, and response strategies for fish, wildlife, and environmental protection.
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United States Office of Emergency EPA 540-K-99- Environmental Protection And Remedial OSWER 9200.5-104A Agency Response PB2000- December 1999 Oil Program Center
EPA Office of Emergency and Remedial Response • 1
OIL SPILLS endanger public health, imperil drinking water, devastate natural resources, and disrupt the economy. In an increasingly technological era, the United States has become more dependent upon oil-based products to help us maintain our high standard of living. Products derived from petroleum, such as heating oil and gasoline, provide fuel for our automobiles, heat for our homes, and energy for the machinery used in our industries. Other products derived from petroleum, including plastics and pharmaceuticals, provide us with convenience and help to make our lives more comfortable. Additionally, non-petroleum oils, such as vegetable oils and animal fats, are increasingly being consumed in the United States. These oils can contain toxic components and can produce physical effects that are similar to petroleum oils. Because they have toxic properties and produce harmful physical effects, spills of non-petroleum oils also pose threats to public health and the environment. Because we use vast quantities of oils, they are usually stored and transported in large volumes. During storage or transport, and occasionally as the result of exploration activities, oils and other oil-based products are sometimes spilled onto land or into waterways. When this occurs, human health and environmental quality are put at risk. Every effort must be made to prevent oil spills and to clean them up promptly once they occur. The U.S. Environmental Protection Agency’s Oil Spill Program plays an important role in protecting the environment through prevention of, preparation for, and response to oil spills. Several U.S. EPA offices and other organizations deserve special recognition for their contributions to the revision of this booklet. They are EPA Regions III and V, the EPA Environmental Response Team, the EPA Office of Research and Development, the U.S. Fish and Wildlife Service, the State of Alaska Department of Environmental Conservation, the State of Wisconsin Department of Natural Resources, the University of California Wildlife Health Center, and BP Amoco Corporation. The purpose of this booklet is to provide information about oil spills. It contains chapters that outline and explain oil spills, their potential effects on the environment, how they are cleaned up, and how various agencies prepare for spills before they happen. Details about five oil spills are provided to show different types of spills and the complexities and issues involved in responding to them. This oil spill discussion includes the Exxon Valdez spill of March 1989; the Ashland oil spill of January 1988; the Wisconsin fire and butter spill in May 1991; the Colonial Pipeline spill of March 1993; and the Lake Lanier soybean oil spill in Atlanta in 1994.
4 • Understanding Oil Spills and Oil Spill Response
6 • Understanding Oil Spills and Oil Spill Response
breaking a slick into droplets which are then distributed vertically throughout the water column. These droplets can also form a secondary slick or thin film on the surface of the water.
nitrogen and phosphorus are sometimes added to the water to encourage the microorganisms to grow and reproduce. Biodegradation tends to work best in warm- water environments.
Fate of spilled oil.
EPA Office of Emergency and Remedial Response • 7
SOME TOXIC SUBSTANCES in an oil spill may evaporate quickly. Therefore, plant, animal, and human exposure to the most toxic substances are reduced with time, and are usually limited to the initial spill area. Although some organisms may be seriously injured or killed very soon after contact with the oil in a spill, non- lethal toxic effects can be more subtle and often longer lasting. For example, aquatic life on reefs and shorelines is at risk of being smothered by oil that washes ashore. It can also be poisoned slowly by long-term exposure to oil trapped in shallow water or on beaches.
Both petroleum and non-petroleum oil can affect the environment surrounding an oil spill. All types of oil share chemical and physical properties that produce similar effects on the environment. In some cases, non-petroleum oil spills can produce more harmful effects than petroleum oil spills.
Chapter five discusses in greater detail how oil spills impact wildlife.
Aquatic environments are made up of complex interrelations between plant and animal species and their physical environment. Harm to the physical environment will often lead to harm for one or more species in a food chain, which may lead to damage for other species further up the chain. Where an organism spends most of its time—in open water, near coastal areas, or on the shoreline—will determine the effects an oil spill is likely to have on that organism.
In open water, fish and whales have the ability to swim away from a spill by going deeper in the water or further out to sea, reducing the likelihood that they will be harmed by even a major spill. Aquatic animals that generally live closer to shore, such as turtles, seals, and dolphins, risk contamination by oil that washes onto beaches or by consuming oil-contaminated prey. In shallow waters, oil may harm sea grasses and kelp beds, which are used for food, shelter, and nesting sites by many different species.
Spilled oil and cleanup operations can threaten different types of aquatic habitats, with different results.
Crews work to keep oil from entering a marsh.
EPA Office of Emergency and Remedial Response • 9
TWO MAJOR STEPS involved in controlling oil spills are containment and recovery. This chapter outlines some of the techniques and equipment that are used to conduct oil spill control efforts.
WHEN AN OIL SPILL occurs on water, it is critical to contain the spill as quickly as possible in order to minimize danger and potential damage to persons, property, and natural resources. Containment equipment is used to restrict the spread of oil and to allow for its recovery, removal, or dispersal. The most common type of equipment used to control the spread of oil is floating barriers, called booms.
Containment booms are used to control the spread of oil to reduce the possibility of polluting shorelines and other resources, as well as to concentrate oil in thicker surface layers, making recovery easier. In addition, booms may be used to divert and channel oil slicks along desired paths, making them easier to remove from the surface of the water.
Although there is a great deal of variation in the design and construction of booms, all generally share four basic characteristics:
Booms can be used to control the spread of oil.
10 • Understanding Oil Spills and Oil Spill Response
Booms can be fixed to a structure, such as a pier or a buoy, or towed behind or alongside one or more vessels. When stationary or moored, the boom is anchored below the water surface.
It is necessary for stationary booms to be monitored or tended due to changes produced by shifting tides, tidal currents, winds, or other factors that influence water depth and direction and force of motion. People must tend booms around the clock to monitor and adjust the equipment.
The forces exerted by currents, waves, and wind may impair the ability of a boom to hold oil. Loss of oil occurring when friction between the water and oil causes droplets of oil to separate from the slick and be pulled under the boom is called entrainment. Currents or tow speeds greater than three-quarters of a knot may cause entrainment. Wind and waves can force oil over the top of the boom’s freeboard or even flatten the boom into the water, causing it to release the contained oil. Mechanical problems and improper mooring can also cause a boom to fail.
While most booms perform well in gentle seas with smooth, long waves, rough and choppy water is likely to contribute to boom failure. ln some circumstances, lengthening a boom’s skirt or freeboard can help to contain the oil. Because they have more resistance to natural forces such as wind, waves, and currents, oversized booms are more prone to failure or leakage than smaller ones. Generally, booms will not operate properly when waves are higher than one meter or currents are moving faster than one knot per hour. However, new technologies, such as submergence plane booms and entrainment inhibitors, are being developed that will allow booms to operate at higher speeds while retaining more oil.
When a spill occurs and no containment equipment is available, barriers can be improvised from whatever materials are at hand. Although they are most often used as temporary measures to hold or divert oil until more sophisticated equipment arrives, improvised booms can be an effective way to deal with oil spills, particularly in calm water such as streams, slow-moving rivers, or sheltered bays and inlets.
Improvised booms are made from such common materials as wood, plastic pipe, inflated fire hoses, automobile tires, and empty oil drums. They can be as simple as a board placed across the surface of a slow-moving stream, or a berm built by bulldozers pushing a wall of sand out from the beach to divert oil from a sensitive section of shoreline.
ONCE AN OIL SPILL has been contained, efforts to remove the oil from the water can begin. Three different types of equipment— booms, skimmers, and sorbents —are commonly used to recover oil from the surface.
When used in recovering oil, booms are often supported by a horizontal arm extending directly off one or both sides of a vessel. Sailing through the heaviest sections of the spill at low speeds, a vessel scoops the oil and traps it between the angle of the boom and the vessel’s hull. ln another variation, a boom is moored at the end points of a rigid arm extended from the vessel, forming a ”U”- or “J”- shaped pocket in which oil can collect. In either case, the trapped oil can then be pumped out to holding tanks and returned to shore for proper disposal or recycling.
A skimmer is a device for recovery of spilled oil from the water’s surface. Skimmers may be self-propelled and may be used from shore or operated from vessels. The efficiency of skimmers depends on weather conditions. In moderately rough or choppy water, skimmers tend to
Oleophilic skimmer.
Suction skimmer.
Photo courtesy of RO-CLEAN DESMI
Photo courtesy of RO-CLEAN DESMI
12 • Understanding Oil Spills and Oil Spill Response
THE PRIMARY tools used to respond to oil spills are mechanical containment, recovery, and cleanup equipment. Such equipment includes a variety of booms, barriers, and skimmers, as well as natural and synthetic sorbent materials. A key to effectively combating spilled oil is careful selection and proper use of the equipment and materials most suited to the type of oil and the conditions at the spill site. Most spill response equipment and materials are greatly affected by such factors as conditions at sea, water currents, and wind. Damage to spill- contaminated shorelines and dangers to other threatened areas can be reduced by timely and proper use of containment and recovery equipment.
THIS EXPERIMENT is designed to help you to understand the difficulties with oil spill cleanups. You will need the following equipment:
EPA Office of Emergency and Remedial Response • 13
SEVERAL METHODS exist for containing and cleaning up oil spills in aquatic environments. Chapter two describes how mechanical equipment, such as booms and skimmers , is used to block the spread of oil, concentrate it into one area, and remove it from the water. Chemical and biological treatment of oil can be used in place of mechanical methods, especially in areas where untreated oil may reach shorelines and sensitive habitats where a cleanup becomes difficult and environmentally damaging. This chapter describes some of the chemical and biological methods that are used by response personnel to contain and clean up oil spills in aquatic environments. Alternative treatment typically involves adding chemical or biological agents to spilled oil and also includes in-situ burning.
TWO TYPES of substances commonly used in responding to an oil spill are (1) dispersing agents and (2) biological agents.
Dispersing agents, also called dispersants , are chemicals that contain surfactants , or compounds that act to break liquid substances such as oil into small droplets. In an oil spill, these droplets disperse into the water column, where they are subjected to natural processes—such as wind, waves, and currents—that help to break them down further. This helps to clear oil from the water surface, making it less likely that the oil slick will reach the shoreline.
The effectiveness of a dispersant is determined by the composition of the oil it is being used to treat and the method and rate at which the dispersant is applied. Heavy crude oils do not disperse as well as light- to medium- weight oils. Dispersants are most effective when applied immediately following a spill, before the lightest components in the oil have evaporated.
Environmental factors, including water salinity and temperature, and conditions at sea influence the effectiveness of dispersants. Studies have shown that many dispersants work best at salinity levels close to that of normal seawater. While dispersants can work in cold water, they work best in warm water.
Some countries rely almost exclusively on dispersants to combat oil spills because frequently rough or choppy conditions at sea make mechanical containment and cleanup difficult. However, dispersants have not been used extensively in the United States because of difficulties with application, disagreement among scientists about their effectiveness, and concerns about the toxicity of the dispersed mixtures. Dispersants used today are much less toxic than those used in the past, but few long-term environmental effects tests have been conducted after a dispersant application. The EPA encourages the monitoring of areas that may see increased dispersant use.
Helicopters are often used to apply dispersants to large areas.
EPA Office of Emergency and Remedial Response • 15
type, water level, erosion potential, vegetation species and condition, and wildlife species presence. Burning may actually allow oil to penetrate further into some soils and shoreline sediments.
Because it releases pollutants into the air, in-situ burning requires careful air quality monitoring. Devices are pre- deployed near populations to measure particulate levels. If air quality standards are exceeded, the burn will be terminated.
Because in-situ burning uses intense heat sources, it poses additional danger to response personnel. Igniting an oil slick requires a device that can deliver an intense heat source to the oil.
Vessel-deployed ignition devices are soaked with a volatile compound, lit, and allowed to drift into an oil slick. During the Exxon Valdez cleanup effort, plastic bags filled with gelled gasoline were ignited and placed in the path of oil being towed in a containment fire-boom. Hand-held ignition systems can be thrown into oil slicks but require personnel to be in close proximity to the burning oil. A recently developed ignition device called the “Helitorch,” delivers a falling stream of burning fuel from a helicopter, allowing personnel to maintain a safer distance from the burning slick and distribute ignition sources over a wider area.
Although it can be effective in some situations, in-situ burning is rarely used on marine spills because of widespread concern over atmospheric emissions and uncertainty about its impacts on human and environmental health. However, burning of inland spills is frequently used in a number of states. All burns produce significant amounts of particulate matter, dependent on the type of oil being burned. Burning oil delivers polycyclic aromatic hydrocarbons, volatile organic compounds, carbon dioxide, and carbon monoxide into the air in addition to other compounds at lower levels. In addition, when circumstances make it more difficult to ignite the oil, an accelerant such as gasoline may need to be added, possibly increasing the toxicity of the volatilizing particles. Lack of data regarding the environmental and human health effects of burning has also discouraged its use.
In-situ burning will be used more often as federal response agencies learn from its behavior and effects. As in the case of the New Carissa , a Japanese freighter that ran aground at the entrance to Coos Bay in Oregon on February 4, 1999, the conditions were favorable for burning. The ship was carrying approximately 360,000 gallons of bunker fuel. Early assessment of the vessel revealed that it was leaking fuel. In order to reduce the potential for oil to spill from the vessel during impending storms, responders ignited the grounded ship with incendiary devices in an attempt to burn the fuel in the cargo holds.
Despite its drawbacks, in-situ burning may be an efficient cleanup method under certain conditions where there are few negative effects on humans or the environment. These
conditions include remote areas, areas with herbaceous or dormant vegetation, and water or land covered with snow or ice. In these circumstances, burning can quickly prevent the movement of oil to additional areas, eliminate the generation of oily wastes, provide a cleanup means for affected areas with limited access for mechanical or physical removal methods, or provide an additional level of cleanup when other methods become ineffective. When oil is spilled into water containing a layer or chunks of ice, burning can often remove much more oil than conventional means. Burning can also help to eliminate some volatile compounds that might otherwise evaporate off a slick. Although limited, research and development for in-situ burning in the areas of training, fire-resistant booms, and ignition systems have increased in recent years. Investigation into inland environments and vegetative species that are more tolerant of burns is also yielding results which can aid responders. As data regarding the effects of burning oil on the environment and human population increase, consideration and use of in-situ burning may become more frequent when spills occur.
CHEMICAL AND BIOLOGICAL methods can be used in conjunction with mechanical means for containing and cleaning up oil spills. Dispersants are most useful in helping to keep oil from reaching shorelines and other sensitive habitats. Biological agents have the potential to assist recovery in sensitive areas such as shorelines, marshes, and wetlands. In-situ burning has shown the potential to be an effective cleanup method under certain circumstances. Research into these technologies continues in the hope that future oil spills can be contained and cleaned up more efficiently and effectively.
In-situ burning can remove oil quickly.
Photo courtesy of MMS
16 • Understanding Oil Spills and Oil Spill Response
18 • Understanding Oil Spills and Oil Spill Response
aggressive cleanup than those from lighter ones. Shoreline clean-up of inland spills usually involves lighter oils. Inland oil spills often involve refined petroleum products, although spills of other types of oil are not uncommon. Spills in marine ecosystems often involve crude oils and heavy fuel oils originating from accidents during tanker operations.
Shorelines can vary dramatically in their forms and compositions. Some marine shorelines are narrow, with beaches formed from rounded or flattened cobbles and pebbles; some are wide and covered in a layer of sand or broken shell fragments; and still others are steep cliffs with no beach at all. Generally, freshwater shorelines are composed of sediments and may be lined with trees or heavy vegetation. The composition and structure of the bank will determine the potential effects of oil on the shoreline.
Oil tends to stick to sediments and to the surfaces of cobbles and pebbles. It also flows downward in the spaces between cobbles, pebbles, and sand grains, and accumulates in lower layers of sediments. Oil that sticks to sediment particles suspended in the water column, or to cobbles and pebbles along the bank, is exposed to sunlight and waves, which help it to degrade and make it less hazardous to organisms that come into contact with it. Oil that sticks to rocks and pebbles can be wiped or washed off. Oil that flows onto sandy banks, however, can “escape” downward into sand, making it difficult to clean up and reducing its ability to degrade.
The effects of an oil spill on marine and freshwater habitats varies according to the rate of water flow and the habitat’s specific characteristics. Standing or slow-moving water, such as marshes or lakes, are likely to incur more severe impacts than flowing water, such as rivers and streams, because spilled oil tends to “pool” in the water and can remain there for long periods of time. In calm water
conditions, affected habitats may take years to recover. When oil spills into a flowing river, the impact may be less severe than in standing water because the river current acts as a natural cleaning mechanism. Currents tend to be the strongest along the outside edge of a bend in a river where the current tends to flow straight into the outside bank before being deflected downstream. Oil contamination is usually heavy in this area because currents drive the oil onto the bank. In marine environments and on large lakes and rivers, waves affect the movement and spreading of oil spills in several different ways. Initially, the oil spreads to form a thin film, called an oil slick. The slick appears smooth compared to the water around it. Momentum is then transferred from the waves to the oil slick. Small waves tend to push oil slicks in the direction of wave propagation. This makes oil slicks move slightly faster than the surface of the water that they are floating on. Short, relatively steep waves can result in a surface current that will move the oil in a downwind direction. As waves break, the resulting plunging water creates a turbulent wake, carrying particles of oil down into the water column.
Biological communities differ in their sensitivity to oil spills and the physical intrusion that may be associated with various cleanup methods. Some ecosystems seem to recover quickly from spills, with little or no noticeable harm, while others experience long-term harmful effects. Animals and plants may be affected by the physical properties of spilled oil, which prevent respiration, photosynthesis, or feeding. Animals, such as elephant seals, which depend on the marine environment for breeding and pupping, can lose their ability to stay warm in cold water when their skin comes into contact with oil. Birds lose their ability to fly and to stay warm when their feathers are coated with oil, and fish can suffocate when their gills are covered with oil. An oil spill can disrupt an ecosystem’s food chain because it is toxic to some plants which other organisms may depend on for food. In addition, oil in sediments like those that are common in freshwater shorelines may be very harmful because sediment traps the oil and affects the organisms that live in, or feed off, the sediments.
BOTH NATURAL processes and physical methods aid in the removal and containment of oil from shorelines. Sometimes physical methods are used to enhance naturally occurring processes. Examples of a technology that uses both natural processes and physical methods to clean up an oil spill are biodegradation and bioremediation , which are described later.
The type of environment needs to be considered when devising a cleanup plan.
EPA Office of Emergency and Remedial Response • 19
Natural processes that result in the removal of oil from the natural environment include evaporation, oxidation , and biodegradation.
Evaporation occurs when liquid components in oil are converted to vapor and released into the atmosphere. It results in the removal of lighter-weight substances in oil. In the first 12 hours following a spill, up to 50 percent of the light-weight components may evaporate. Since the most toxic substances in oil tend to be those of lightest weight, this evaporation decreases the toxicity of a spill over time.
Oxidation occurs when oxygen reacts with the chemical compounds in oil. Oxidation causes the complex chemical compounds in oil to break down into simpler compounds that tend to be lighter in weight and more able to dissolve in water, allowing them to degrade further.
Biodegradation occurs when naturally occurring bacteria living in the water or on land consume oil, which they can use to provide energy for their various biological needs. When oil is first spilled, it may be toxic to some bacteria, which makes the initial rate of biodegradation quite slow. As the oil evaporates and the more toxic substances are removed, the population of bacteria grows and biodegradation activity accelerates.
In nature, biodegradation is a relatively slow process. It can take years for a population of microorganisms to degrade most of the oil spilled onto a shoreline. However, the rate at which biodegradation occurs can be accelerated by the addition of nutrients, such as phosphorus and nitrogen, that encourage growth of oil-degrading bacteria. This process is called biostimulation. Biodegradation rates can also be increased by adding more microorganisms to the environment, especially species that are already used to consuming the type of oil spilled. Adding microorganisms is referred to as bioaugmentation. The use of nutrients or the addition of microorganisms to encourage biodegradation is called bioremediation.
When oil spill response personnel develop bioremediation strategies, they have to consider the effects of waves, tides, and currents on the nutrients and microorganisms they are applying to oil-contaminated areas. Contamination of coastal areas by oil from offshore spills usually occurs in the intertidal zone where waves and tides can quickly carry away dissolved nutrients. Adding nutrients may not be effective on beaches with a great deal of wave action and tidal flows because most of the nutrients will be lost to dilution. On calmer shorelines, adding nutrients may be an effective bioremediation strategy.
With respect to freshwater shorelines, an oil spill is most likely to have the greatest impact on wetlands or marshes rather than on a wide shoreline zone like a marine intertidal zone. Less research has been conducted in these types of environments, so it is not yet known how well bioremediation enhances oil removal. The same principals apply to this environment as a marine environment,
namely, that nutrients should be applied in ways that will keep them from washing away from the affected areas long enough to affect the enhanced treatment. In wetlands, bioremediation may not work as well because there is less oxygen in the sediments than there is on a sandy beach; even with added nutrients, microorganisms may not have enough oxygen to effectively combat the spill. EPA is currently studying the biodegradability of non- petroleum oils (vegetable oils and animal fats) and their impacts on freshwater and marine environments during biodegradation. Chapter three discusses bioremediation and other alternative cleanup approaches.
Physical removal of oil from shorelines, and especially beaches, is time-consuming and requires much equipment and many personnel. Methods used to physically clean oil from shorelines include the following:
Wiping with Absorbent Materials Materials that are capable of absorbing many times their weight in oil can be used to wipe up oil from contaminated shorelines. These materials are often designed as large squares, much like paper towels, or shaped into “mops.” The squares or mops are used to wipe the shoreline or oily rocks during which time the absorbents are filled with as much oil as they can hold. There are advantages to the use of absorbents. They can be used to clean up any kind of oil on any shoreline that can be reached by response personnel. The use of absorbents is generally not harmful to the shoreline itself or to the organisms that live on it, and no material is left behind following the cleanup effort. Some sorbents are reusable, reducing the need for disposal after a spill. Wiping with absorbent materials requires the use of a large quantity of material and several personnel. Personnel must wear proper protective clothing to minimize direct contact with the oil as they are removing it. Oil-filled absorbents and protective clothing that are used by response personnel must be properly disposed of following cleanup, which can be costly. In addition, the intrusion of many people onto an isolated shoreline may disrupt animal behaviors such as breeding or nesting.
