Arctic Oil Spill Recovery Operations: Technology and Tactics

(from AMSA Report 2009)

Effective Arctic oil spill recovery operations require advanced planning and international cooperation. All available methods must be available and considered for each situation although some methods have proven more effective in ice-covered waters. Along with planning and cooperation, training, incident communications and risk management are key elements to any oil recovery operation.

Mechanical recovery techniques combined with oil detection and tracking methods, currently dominate the in-field capabilities of most nations. However, tracking, detecting, as well as modeling oil in ice-covered waters has inherent environmental limitations. The mechanical methods are often considered the most environmentally friendly recovery methods. The concept is to create barriers via floating or alternative booms, recover the oil out of the sea with a mechanical skimmer and then do the post-treatment for the recovered oil in a controlled manner in environmentally safe conditions. However, the mechanical methods are laborious and time consuming and their efficiency is low. Further, mechanical methods often require complicated logistical support in the form of equipment and personnel transportation, which in remote or harsh conditions cannot easily be provided. Mechanical recovery in ice and snow conditions must meet challenges in terms of booming, skimming, recovery and pumping capabilities. Each of these areas has specific challenges to optimum recovery efforts.

Chemical dispersion can be utilized to promote the formation of oil droplets in order to accelerate the natural dispersion and biodegradation of spilled oil. Dispersants (surfactants) can be applied to control offshore slicks or oil that accumulates in coastal areas that have significant tidal or flushing action. In order for dispersion to be effective there needs to be limited weathering of the spilled oil, a cohesive slick, an oil within the viscosity ranges of dispersibility, an appropriate dispersant to oil ratio and turbulent mixing. Only a few research studies have been performed in the past 20 years regarding the use of dispersants on oil spills in ice-infested waters, either from an effectiveness or environmental-impact perspective, and these are of limited value in assessing the situation in realistic terms. Logistical support and effectiveness may also be a challenge when using dispersants. Limited studies such as the Joint Industry Program (JIP) on Oil in Ice, have followed the long-term fate of dispersed oil, but most impacts have been derived from laboratory studies.

In-situ burning, or ISB, is a treatment method that can be used for oil on open water, on ice and in broken ice, if adequate oil thickness can be achieved to sustain burning. This may require the use of booms or herding agents. While continued studies are needed to best determine the ISB effectiveness window of opportunity, for in-situ burning to be a viable option, planning, special equipment and training specific to ISB must be in place before the limited window of opportunity presents itself during a spill. Burnability is a function of oil type (chemical/physical factors), oil thickness on the interface and its state of weathering/degradation. While colder Arctic temperatures are a force to overcome for ISB in ice-covered waters, other natural degradation processes such as slower rates of spreading, evaporation and emulsification have supported burning.

From the recovery rate point of view, in-situ burning seems to be the most effective method for clean-up of oil spills in ice and snow conditions. Furthermore, removal efficiency exceeding 90 percent can be achieved in ideal conditions (open water, fire booms and quiet conditions), but a burning rate of 60 to 70 percent can be considered as representative for burning on ice-free water. The burning rate can also be zero percent if the oil is not ignitable. ISB may be more limited due to weathering of the oil than the use of dispersants. This is significantly more effective than rates of 10 to 20 percent for mechanical recovery. Alternatively, in-situ burning will generate smoke and soot, thus moving part of the pollution from the sea to the air, and will leave a burn residue that must be recovered. Monitoring and assessment of these results is always necessary.

Oil may be removed by biological degradation. Oil-degrading bacteria naturally exist in the seas with oil, including the cold and icy waters. By adding oxygen and/or nutrients and/or bacteria a possible acceleration of this fundamentally natural process can occur. While bioremediation is an effective countermeasure for small spills with high surface areas (e.g., very thin staining or coating on shorelines), it is a relatively slow process, possibly requiring months if not years to fully accomplish and is best suited for post-spill response final treatment.

Arctic Council, 2009, Arctic Marine Shipping Assessment (AMSA), Arctic Council.©