New Regulation of Ocean Dumping: Discharged Ballast Water Must Be Clean

By Joel C. Mandelman
March 04, 2006
Every oil tanker, freighter and cruise ship carries ballast water. A typical oil tanker will carry as much as 20 million gallons of ballast water and a freighter, depending on its size, from 6 to 10 million gallons. As cargo is taken on board an equivalent weight in ballast water must be discharged, so that the vessel remains stable. When cargo is unloaded, the process is reversed. Without ballast water, a ship will become dangerously unstable, unable to operate efficiently and it may even capsize and sink. The preferred place to discharge ballast water is while the vessel is in port. But most nations no longer allow ships to do that. They now require that the ballast water be exchanged, typically 200 miles off shore, before the vessel enters a port. The theory underlying this practice is that the exchanged ballast water is cleaner.Unfortunately, it is usually not appreciably cleaner than the sea-water for which it is exchanged. Such ballast water will probably contain almost as many invasive species by the time the ship reaches port as a ship that never conducted a deep ocean exchange....