Starting this year, single-hulled oil tankers are now illegal in all U.S. waters.
The Oil Pollution Act of 1990, passed after the 1989 Exxon Valdez oil spill, required that all new oil tankers be constructed with double hulls. Single-hulled tankers were allowed to continue operating, but were to be gradually phased out.
The Act set a deadline for this phase-out, requiring all single-hulled tankers to be removed from service by January 1, 2015.
Double hulls are basically two steel skins, separated by several feet of space, providing a buffer between the oil and the environment. Double hulls have reduced or eliminated spills resulting from groundings or collisions.
The deadline is not a major change, since the implementation of double hull requirements were required internationally between 2007 and 2012, and phased in under the Act between 2010 and 2015. As a result, most tankers in U.S. waters, and all oil tankers in Prince William Sound, have had double hulls for several years.