Enactment of the Oil Pollution Act of 1990 has resulted in increased efforts by the U.S. Coast Guard to identify and evaluate existing tanker routing schemes that may pose a threat to sensitive marine resources. The Minerals Management Service is assisting in these efforts through stochastic applications of its oil spill trajectory models. Restricting tanker routes or establishing tanker-free zones would constrain the potential sites of future tanker spills. This restriction would maximize the available response time for containment, recovery, or natural dispersion of tanker spills. Two analyses are described.

In the first analysis, multiple trajectories were simulated from tanker routes off the U.S. west coast. (Similar analyses are planned for the east coast and the Gulf of Mexico.) Contacts with environmental resources, which were assigned sensitivity index values, were plotted as seasonal oil spill contact risk contours. The contours were used to define alternative boundaries of potential tanker-free zones. These alternative boundaries, in turn, may provide specified levels of protection for sensitive marine areas.

The second application of oil spill simulations is in the Gulf of Mexico, where the U.S. Coast Guard is evaluating the potential impact of establishing tanker lightering zones. These lightering zones would concentrate traffic in certain areas where large vessels would offload petroleum cargo into smaller tankers for transport ashore. Results of the oil spill trajectory model characterize the risks from these zones.

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