Oil Spill Prevention and Liability Act of 2004 - Amends the Oil Pollution Act of 1990 to double liability limits associated with oil spills for double-hull tank vessels, other vessels, offshore facilities (except deepwater ports), and onshore facilities and deepwater ports.
Gradually phases out (over six years) liability limits for single-hull vessels.
Authorizes the Secretary of the department in which the Coast Guard is operating to establish separate liability limits for the transportation of oil by vessel to deepwater ports.
Amends the Ports and Waterways Safety Act to require the Secretary to promulgate regulations under which port owners or operators may place restrictions on the entry of tank vessel shipments presenting a risk of severe harm to the port or port region.
Requires single-hull tank vessels that are more than 15 years old to undergo annual inspections.
Directs the Commandant of the Coast Guard to contract with the National Academy of Sciences for a study assessing the total economic cost of oil spills, and the types of costs resulting from such spills, and to report the findings to Congress.