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| This document contains information on Response Strategies and Considerations, including: Environmental Considerations; Strategies of Oil Spill Response; Chemicals and Their Use; and Fate and Effects of Spilled Oil. |
| Because human error causes 46% of oil spills and equipment failure 34% the first strategy must be that of PREVENTION. However, assuming that in the particular case prevention has not been effective the remaining strategic options are: |
| Contain and Recover |
| Containment and Recovery removes the pollutant from the environment by mechanical means. This strategy has the following characteristics: |
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| The usual method of containment and recovery involves deploying booms to prevent the oil from spreading and to concentrate it. Skimmers are then used to recover the concentrated oil. It is then transferred to temporary storage and eventually to a permanent storage/treatment facility. When employing this strategy it is necessary to consider the following questions: |
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| Dispersion |
| Natural Dispersion - When a great deal of mixing energy is applied at the oil-water interface, i.e. such as a rough sea surface, the oil and water becomes emulsified and may disperse naturally. |
| Dispersant
- Using a dispersant as a strategy involves the use of chemicals
to speed up the process of natural dispersion. FEDERAL AUTHORIZATION
MUST BE OBTAINED IN EACH CASE BEFORE THE USE OF DISPERSANTS. Dispersants
act in the same way as household detergents; when they are added
to a film of oil on the surface of the water the oil breaks up into
very small droplets forming thin emulsions which disperse in the
water column. In effect, they speed up the natural processes of
dispersion. In dispersed form the oil is subject to degradation
by micro-organisms which occur naturally in the sea. A characteristic
plume can be seen spreading slowly down the water surface shortly
after treatment if an oil has been satisfactorily dispersed. Dispersants
do not destroy the oil. However, this must be weighed against the
fact that dispersing the oil in the water column makes its toxic
components more readily available to marine organisms, particularly
in shallow water. Dispersants do not work on all types of oil or in cold weather conditions under which oil tends to become very viscous. Evaporation and emulsification which render oil resistant to dispersant occur over time and in most cases, dispersant will likely be ineffective after a day or two. If the oil is very viscous (thick) dispersants are ineffective, since they tend to run off the oil into the water before they can penetrate. As a general rule, dispersants can be effective in dispersing most liquid oils and liquid water-in-oil emulsions with viscosities less than about 2000 centistokes. Oils that may be more susceptible to treatment on first entry to the water become progressively less so as mousse forms or weathering takes place. |
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There are several Dispersant application methods:
The method of application depends primarily on the type of dispersant, the size and location of the spill, and the availability of vessels or aircraft for spraying the dispersant. You might want to take a look at drawings of some of the various dispersant application systems. (Note: This page has several large graphics and will take a while to load.) For a dispersant application to be effective several factors in addition to the type of dispersant being used need to be considered because they control the dispersant to oil application ratio; the vessel or aircraft speed, the swath width (path covered by the spray pattern), the size and number of the spray nozzles, and the thickness of the oil.
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| In-situ Burn |
| In-situ
Burning involves igniting the oil on the surface of the water works
well in removing large quantities of spilled oil from the water.
To be successful, this is a strategy best initiated early prior
to evaporation of the lighter ends which support combustion and
prior to weathering of the oil. In-situ burning can only be done in open waters where no danger is posed to drilling rigs, ships, or shoreline. Fire boom is used to corral the oil and contain it during the burn. Obviously some air pollution does occur when oil is burned.
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| Do Nothing |
| To
Do Nothing is a strategy seldom used and is difficult to justify.
However, this strategy may sometimes be appropriate. No action is
taken except for monitoring the movement of the spilled oil. Natural
and biological processes will disperse most spills given time. Crude
oils, particularly of the lighter kinds, that have been spilled
a considerable distance offshore in the rough conditions characteristic
of those waters are unlikely to pose an environmental threat unless
in close proximity to vulnerable concentrations of sea birds. There
is a likelihood that these oils will be dispersed by natural processes
before reaching shore.
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| Beach Clean-Up |
| Beach Clean-up. In some cases, despite all the efforts to deal with spilled oil offshore, some oil still reaches the shore. Or it may be an acceptable strategy depending upon the circumstances to allow the oil to come ashore for subsequent collection. In these instances the principal means of cleaning up the oil becomes physical. Beach clean up is labor intensive. The tools used include buckets, shovels, skimmers, booms, earth moving equipment, pumps, vacuum equipment, absorbents, and temporary storage. If the beach has not been cleaned prior to oil impact, oiled debris must be disposed of along with oil and oiled sand. |
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| CHEMICALS AND THEIR USE |
| Chemicals used to treat oil spills include the following:
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| FATE AND EFFECTS OF SPILLED OIL (Click On An Image To Enlarge) |
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