Offshore oil-spill occurrence rates

The U.S. Minerals Management Service maintains statistics on the frequency of offshore oil spills associated with platforms, pipelines, and tanker traffic. Oil-spill occurrence rates have decreased slightly for U.S. offshore platforms, increased for U.S. offshore pipelines, and remained about the same for worldwide tankers (comparing rates calculated through 1992 to rates calculated through the mid-80s). Recently calculated rates are presented for tanker spills occurring during transport of Alaskan North Slope (ANS) crude oil after offloading from the Trans-Alaska Pipeline at Valdez. These rates are being used in environmental analyses of risks associated with the recently legislated exporting of ANS oil to the Far East. The use of spill statistics for such analyses is described, along with major assumptions and limitations of the methodology