The probable cause of the spill was the failure of the third mate to properly maneuver the vessel because of fatigue and excessive workload. Other contributing factors were one, the failure of the master to provide a proper navigational watch because of impairment from alcohol, two, the failure of the Exxon Shipping Company to provide sufficient crew for the Exxon Valdez, and three, the lack of an effective Vessel Traffic Service because of inadequate equipment and manning levels.