Configuration for
ocean vessels, usually those that carry
oil, designed to minimize
spillage in case of a
puncture (the type of damage that causes 70% of
maritime oil disasters). After the
Exxon Valdez ran aground in
Prince William Sound in March
1989, spilling more than 11 million gallons of oil into
Alaska waters, the
Oil Pollution Act of 1990 and various international maritime regulations that followed mandated that all ships used to transport oil will have double hulls by the year
2020. (Well, you can't tell companies what kind of equipment to use in their operations, but when the US declares that single hulled vessels won't be allowed in their
territorial waters....) Of course, it is possible to design a double hulled
oil tanker that still leaks when punctured-- an option if you wanted to obey the
letter of the law yet minimize costs (9-17% in building; 5-13% in operating; more for
retrofitting
domestic tankers--'course you could pass that 10 cents a
barrel onto your consumers) by leaving out a few
bulkheads. (A tanker also needs longitudinal subdivision through the
cargo tanks for the double hull design to be safer)
Source: Wolcott, et. al., Double Hull Tanker Legislation: An Assessment of the Oil Pollution Act of 1990, National Academy Press, 1998.