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NOAA publishes AK oil spill risk report Agency considered risks associated with shipping, oil development and other activities in 14 regions offshore the Alaska coastline Alan Bailey Petroleum News
Since the 1989 Exxon Valdez disaster fouled the pristine environment of Alaska’s Prince William Sound, the possibility of another offshore oil spill calamity has become a subject of sometimes heated debate, as well as being a major factor in the slowing of new moves to explore in the seas around the Alaska coast. But what are the odds of future oil spills happening? And what risk might these spills pose to Alaska’s ocean environment?
In an attempt to put some objectivity around answers to these questions and hence provide some strategic guidance to those involved in planning for future oil spill responses, the National Oceanic and Atmospheric Administration, or NOAA, has carried out a comprehensive analysis of oil spill risks in the Alaska offshore and has now published a report on the results of that study.
Defining oil spill risk as a combination of the probability of a spill happening and the scale of the negative consequences of the accident, NOAA considered spills that might result from a number of operations, ranging from marine shipping to offshore oil exploration.
“Alaska’s waters are rich in biological resources that are sensitive to spilled oil,” the report says in its introductory paragraph. “These waters are also host to oil exploration/production activities and heavy vessel traffic, and are bordered by land-based facilities that transfer, store and handle oil.”
14 regional zones The risk model presented in the report considers the Alaska offshore as 14 broad geographic zones, ranging from the Chukchi Sea and the Beaufort Sea in the north to the Aleutians in the south. Zones in southern Alaska include the Cook Inlet and Prince William Sound regions. Within each of the zones the model encompasses six two-month seasonal periods spanning an entire year, while considering four general oil types that may be spilled: crude oil, heavy oil, light oils and distillates.
Within each geographic zone and seasonal period, and for each oil type, the analysis considers the scales of possible oil spills in terms of both the maximum most probable discharge and a worst case discharge. The “maximum most probable discharge” is a term used by the U.S. Coast Guard, for example, to specify a maximum volume of oil likely to be spilled as a result of some specific type of accident. A “worst case discharge” is the most oil likely to be spilled as a result of an accident, assuming efforts to halt the spill fail.
The analysts used oil spill data from 1995 to 2012 to assess the probabilities of different types of spills in different geographic zones for different times of the year. Then, using a literature review of future spillage risk, the analysts assessed what the probabilities would be in 2025, taking into account factors such as anticipated changes in offshore activity and changing risk mitigation technologies.
To model the environmental vulnerabilities of different geographic zones, the analysis assigned vulnerability scores to major natural habitat types and to a variety of wildlife species.
Areas of greatest risk In terms of the potential impacts of maximum most probable discharges on the environment, the study found that, on average across the year, southeast Alaska, the Aleutian region and the Kodiak/Shelikof Strait region are currently at greatest risk, a result that presumably reflects the amount of vessel traffic in these regions. Cook Inlet and Prince William Sound come fairly high in the list. The Beaufort and Chukchi seas come in the middle, while the least risky regions are Western Alaska, Bristol Bay and the Kotzebue Sound/Hope Basin.
Moving forward to 2025, the Beaufort Sea jumps to the top of the list, followed by the Aleutians. This result reflects an expectation of increased oil exploration and production in the Beaufort, and of an increase in vessel traffic around the Aleutians. Curiously, the Chukchi Sea remains in the middle of the list, with the analysis assuming oil and gas development in this region but a relatively low oil-spill incident rate.
Worst case discharge risks Looked at from the perspective of current worst case discharge risks, the Aleutian region moves down toward the middle of the risk ratings, with other regions remaining at somewhat similar relative risks to the maximum-most-probable-discharge ratings. In 2025 the Beaufort Sea moves to the top of the risk table, based on assumptions about future oil industry activities, with the Aleutian region coming second. However, the inferred worst-case risk levels for 2025 drop somewhat in some regions, on the assumption of improved oil spill mitigation measures by that time.
The NOAA report recommends further study into the oil spill risk issues relating to Southeast Alaska, the Aleutians, the Beaufort Sea, the Kodiak/Shelikof Strait and Cook Inlet, the regions identified as having relatively high risk.
“In particular (oil) trajectory and fates modeling would be a natural next step to this study to examine the magnitude of potential consequences from oil spills originating from the high relative risk regions,” the report says.
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