IMO Readies Guide on Spill Response in Ice

The IMO’s third session of the Sub-Committee on Pollution Prevention and Response has agreed to submit a final draft of the Guide to Oil Spill Response in Snow and Ice Conditions to the Marine Environment Protection Committee meeting (MEPC 70) to be held in October, with a view to securing its approval and subsequent publication.

The guide, produced by Owens Coastal Consultants and DF Dickins Associates, both of the U.S., highlights the need to have a rigorous, scientifically defensible process in place for approving the use of dispersants and in situ burning. Any significant ice concentrations can severely limit the effectiveness of mechanical methods for containment and recovery, and the presence of ice can potentially increase the window of opportunity for successful burning and dispersant use (that period when the oil remains unemulsified, has a low viscosity, and is relatively fresh).

Giving responders the flexibility to rapidly select and apply the most effective and environmentally beneficial strategy is crucial to ensuring success of any spill response; linked with the need for thorough contingency planning and drills in advance, states the report.

Mechanical Methods

Mechanical containment and recovery is often preferred over other oil spill countermeasures because it is viewed as directly removing oil from the marine environment. However, the recent experience with using mechanical recovery on an unprecedented scale in the Macondo response highlights a key drawback of mechanical containment and recovery systems when confronted by a large, rapidly spreading oil slick: namely, the encounter rate is insufficient to allow the skimmers to achieve a significant percentage of their theoretical recovery capacity. This problem is amplified greatly by the presence of any significant ice cover.

Another serious drawback in relying on mechanical recovery as a primary response strategy for remote Polar regions is the difficulty in providing the necessary offshore storage to support sustained recovery operations involving large fluid volumes.

Dispersants

Dispersants are designed to enhance natural dispersion by reducing the surface tension at the oil/water interface, making it easier for waves to create small oil droplets (generally less than 100 microns) that are rapidly diluted in the water column, such that natural levels of nutrients can sustain microbial degradation. When used appropriately, dispersants can be an effective oil spill response strategy. They are capable of quickly removing significant quantities of oil from the sea surface by transferring it into the water column where it is broken down by natural processes.

Significant environmental and economic benefits can be achieved, particularly when other at-sea response techniques are limited by weather conditions or the availability of resources. However, as with other response techniques, dispersants also have their limitations and account must be taken of the characteristics of the oil being treated, sea and weather conditions and environmental sensitivities. Each application needs to consider the specific conditions such as water depth, currents, salinity and temperature profiles, and species at risk before making a decision to use dispersants. There is no hard and fast rule in terms of permissible water depth to safely use dispersants – it depends on the particular situation, including consideration of how species could continue to be impacted seriously by oil on the surface or coastlines if dispersants are not used offshore.

Over the past decade, a series of tank and basin tests and field experiments have proven that oil can be dispersed successfully in cold ice covered waters.

The significant contribution of subsea injection of dispersants in the Macondo response in reducing environmental impacts both offshore and on the shorelines provides a new, potentially highly effective response strategy for dealing with future worst-case discharges from Arctic wells. More work needs to be done to assess the short and long-term environmental implications of this technique and to understand all of the physical and biological processes associated with the use of subsea injection in the presence of an ice cover.

Although widely used as the primary means of combatting open water spills by countries such as the U.K., the application of dispersants in an Arctic environment is still highly controversial. The potential to negatively impact local fisheries needs careful consideration in making any decision to use dispersants in areas such as Greenland, Barents Sea and the Bering Sea. Additionally, the application of dispersant directly to the oil and not on adjacent unoiled ice floes needs to be addressed before any use.

In Situ Burning

In situ burning in open water and snow and ice-covered environments is a safe, environmentally acceptable, and proven technique with numerous successful applications in large-scale field experiments and accidental spills over the past 40 years. It is especially suited for use on spills in ice where the ice cover itself often provides a natural barrier to maintain the necessary oil thicknesses for ignition, without the need for booms.

The presence of a minimum oil film thickness for the type of oil (increasing by a factor of ten from light crudes and products to heavy crudes and fuel oils) is the primary limitation governing the success of ignition and burning. Other factors can limit the overall effectiveness, for example the degree of emulsification, waves, strong winds, and slush or brash ice mixed with the oil.

Ongoing research combines the aerial application of proven herding agents and ignitors to create a new rapid response tool for spills in open drift ice where the ice concentrations are insufficient to maintain a burnable film thickness. U.S. Federal and State agencies have developed comprehensive burn guidelines that lay out procedures to avoid any risk to responders or local populations.

There is a large body of research that shows burning to be environmentally safe in terms of smoke particulates and gases, carcinogens (PAHs), and residue aquatic toxicity. In situ burning is not accepted as a permissible or desirable response tool by all Arctic nations or signatories to the Antarctic Treaty. For example, there is no established approval process to implement burning in the Russian Arctic or off Greenland. Implementation of burning has been used in a number of past incidents in the Baltic but it is not viewed generally as a primary response technique.

Spill Hot Spots

Assuming that the potential for spills from vessel accidents are directly related to traffic intensity, the Baltic Sea stands out with the highest risk of any region covered in this Guide in terms of the numbers of vessels engaged in regular operations in ice.

With respect to exploration in the Arctic, planning for the credible worst-case discharge is a primary requirement for new drilling applications but the frequency of such events is extremely remote compared to smaller spills, states the report. In 40 years of offshore drilling in Arctic waters, there has not been a large (over 700 tons) incident. 

Of course, this is no indicator of a future where many more wells could be drilled in these areas, but it does point out that large spills (over 700 tons) occur infrequently. The probability of an extended loss of control event will continue to decrease with improved drilling technologies developed over the past decade. For example, well capping devices engineered following the Macondo incident in 2010 and enhanced blow out preventers in combination with devices such as the Alternative Well Kill System. 

Areas noted in the guide as having the highest current concentration of offshore year-round oil production in ice include: Sakhalin Island, Alaska North Slope, Cook Inlet, Bohai Bay and the Pechora Sea. Most of the presently planned oil exploration programs in areas affected by ice are designed and permitted for completion during the open water period. Spills from those activities are unlikely to occur with ice present under normal circumstances.

The guide is available here.