The impacts of an oil spill are economic, political, and environmental. Oil spills at sea are spread by wind and currents, and when passing close to a coastline, will probably be blown onshore. A shoreline impact is the worst-case scenario and is the driving incentive to respond to a spill and reduce the potential damage. An oil spill that reaches the shoreline can cost multiples of the initial containment response effort. It creates enormous quantities of waste and potential impact to the communities. Preventative action is key to a positive and necessary response to an oil spill.
How are oil spills managed?
There are a number of commonly used response methods:
1. Control the source of the spill
- Repairing the damage vessel / pipe /equipment
- Transferring oil from the vessel / tanks
- For an oil well spill, capping the well or drilling a relief well
2. Containment and recovery of oil from the water surface
Containment and recovery (skimming) a process that recovers spilled oil to be processed on shore. Recovery vessels travel at less than 1 knot and can only skim favourable sea conditions. Though this method is effective on small spills or localised areas of larger and more wide-spread spills, its sole use is limited and very time consuming.
Dispersant can be deployed from vessels or aircraft; aerially deployed dispersants are the most effective method for the delivery of dispersant on large scale oil spills. Chemically treating oil disperses the concentrated spill from the sea surface into the water column. This reduces, if not negates, the chance of the spill being blown onto the shoreline by the wind as the surface oil has been dispersed. The dispersed oil, with a reasonable sea action, will further disperse & naturally biodegrade into the water column, reducing the future potential for environmental damage from the spill. Oil loses its viscosity once dispersed and as such mitigates many of the harmful effects of thick oil in the environment especially those to a shoreline.
Burning can be an effective way to remove oil from the sea surface. Most effectively used on well spills where a constant flow of oil to the surface can be controlled and burnt. The burn must be contained by a fire-resistant boom similar to those used for skimming and therefore have similar restrictions in speed and sea conditions. This limits the surface area that can be burnt to approximately a 40m diameter.