In the Torrey Canyon incident, 41 years ago, environmentally unfriendly 'chemicals' with highly aromatic solvents were used in large quantities. These were highly detrimental to the environment triggering countries to enforce regulations on the use of oil spill treatment chemicals. Organisations which opted to use dispersants faced stringent requirements and in addition, they also faced dispersant toxicity and effectiveness issues and operational challenges.
National government policies may place restrictions on the use of dispersants such and other constraints such as water depth and distance away from sensitive coastlines. They may also maintain a list of approved dispersants which have been tested for efficacy and toxicity which end-users must be aware of and in compliance with.
Besides having to clear the stringent regulations set by the authorities, 'window of opportunity'1 for effective spraying have to be taken into account. These can be identified by laboratory and / or field test under the conditions expected. Key parameters that require consideration are the sea state, water temperature and other environmental conditions 2 that could either enhance or inhibit the process of dispersion
Usage of dispersant during an oil spill response poses certain operational challenges. Issues such as staging and working areas that would offer the shortest possible time must be taken into account. These include distance to the spill site and transit time for the replenishment of dispersant stockpile. Availability of deployment equipment and trained personnel are often logistically challenging and these preparedness issues can lead to an extended response time.
This paper will discuss the key issues and challenges faced during an oil response using dispersant spraying strategy with the aid of case studies from spill response operations in Libya, Korea and Angola.
If spilled oil is dispersible, high volume aerial dispersant application, by virtue of its large encounter rate, is one of the most effective response strategies for dealing with spills in the open marine environment. However, to enable an aerial dispersant operation to be effective, a large number of factors need to be considered in advance.
It is vital to have a comprehensive plan detailing the policy approvals for dispersant use, oil characteristics and environmental data to support their use together with the operational and logistical arrangements to enable their use. Having put all of these preparatory elements in place, the crucial component to ensure a timely and effective response is the need for leadership and rapid decision-making. There are few response strategies that are as time critical for their success as dispersant response and a lack of rapid decision-making can render all of the carefully made preparations invalid.
Over the past twelve months, Oil Spill Response has been involved in three major international responses requiring the use of high volume aerial dispersant system and collectively they have provided lessons in decision-making, technical understanding, legislative recognition, bureaucratic impact, logistics, planning and operational preparedness.