The assessment of risks associated with maritime transportation can be extremely complex. The complexity arises from a multitude of factors. There are currently some 10,000 shipping companies flying the flag of 150 different countries, operating a world commercial shipping fleet of roughly 50,000 vessels. Many of these vessels transit the Aleutian Islands. Regulatory control of these vessels is divided among many entities, including the International Maritime Organization, flag states, port states, and classification societies. Jurisdictional issues are complex—the legal right of transit and the right of innocent passage limit the intervention measures available to state and federal agencies. The quality of vessel design and construction, crew training and experience, and the management standards of operating companies are inconsistent across the fleet. Classes of vessels are designed for specific commodities and services, leading to a large number of ship types and sizes carrying a wide variety of hazardous substances (see Chapter 4). The Aleutian region is subject to severe and highly changeable weather; it is remote, creating challenges for access and communications; and it is home to relatively unspoiled and unique habitats and extensive biodiversity (see Chapter 3).

In view of this complexity, it is appropriate for the risk assessment to begin with qualitative and semiquantitative analyses and assessments and then to focus detailed quantitative assessment on the most significant risks and the more promising risk reduction measures. For this reason, the committee recommends that the study be divided into two phases: a Phase A Preliminary Risk Assessment and a Phase B Focused Risk Assessment. Assessment and prioritization of potential risk reduction measures would be undertaken by the Advisory Panel and Management Team during and immediately after each phase. Technical details and background on each of these steps are provided in Chapter 6.


The proposed risk assessment for shipping operations in the Aleutian Islands specifically addresses the risk of spills from marine vessels transiting through and servicing the region. The recommended bounds for the study are described below.

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