Ocean Dumping and Ship Wastes

This topic deals with ocean dumping and ship wastes, deliberately dumped under controlled conditions. It includes nuclear waste disposal, sewage outfalls, land-based materials or those that derive from shipping, such as from cargo transport ships and passenger ships. For accidental discharge, see Pollution and Degradation.

Internationally, dumping of wastes and other matter is controlled by the London Protocol 1996 to the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter 1972 (the London Convention), administered by the International Maritime Organisation.

The following materials may be dumped under controlled conditions

• dredged material;
• sewage sludge;
• fish wastes;
• vessels and platforms;
• inert, inorganic geological material (e.g., mining wastes);
• organic material of natural origin;
• bulky items primarily comprising iron, steel and concrete; and
• carbon dioxide streams from carbon dioxide capture processes for sequestration (CCS).

About 80-90% of the material dumped at sea results from dredging and currently amounts to hundreds of millions of tons a year. Of the total material dredged, probably two-thirds is associated with operations to keep harbours, rivers and other waterways from silting up. The other third involves new works. Future dredging operations and the requirement for ocean disposal are expected to follow current trends. The ocean disposal of dredged material represents only 20-22% of the total dredged and the remainder is mostly dumped in internal waters, or placed on land for disposal or productive purposes.

Approximately 10% of dredged sediments are heavily contaminated from a variety of sources including shipping, industrial and municipal discharges, and land runoff. Typical contaminants include heavy metals, such as cadmium, mercury and chromium; hydrocarbons, such as oil; organochlorines such as pesticides; and nutrients such as nitrogen and phosphorous. Disposal at sea of these materials carries the possibility of acute or chronic toxic effects on marine organisms, and potential contamination of human food sources.

It was recognized that ships, especially oil powered ships, could cause pollution and both the United Kingdom and the United States introduced legislation in the 1920s to curb discharges of oil resulting from operations such as tank cleaning. Attempts to tackle the problem at an international level were unsuccessful, however, and the outbreak of World War II resulted in the problem being deferred.

The potential for oil to pollute was finally recognised by the International Convention for the Prevention of Pollution of the Sea by Oil 1954. The Convention provided for certain functions to be undertaken by the International Maritime Organization. OILPOL 54 prohibited the dumping of oily wastes within a certain distance from land and in 'special areas' where the danger to the environment was especially acute.