On 20 November 1944, a Japanese manned suicide torpedo struck and sank the US Naval tanker, USS Mississinewa, in 40 meters of water within Ulithi Lagoon in the north-western Pacific Ocean. The tanker was loaded with 19 million litres of aviation and heavy marine fuel oil, most of which was trapped within the wreck, where it lay undisturbed for the next 57 years.
However, on 6 August 2001, a tropical cyclone passing through the pacific disturbed the wreck, causing an estimated 70,000 litres of oil to leak into the lagoon, creating hardship for the 700 islanders that live on the surrounding atoll and rely heavily upon the lagoon's fisheries resources. The leak was eventually plugged by contractors to the US Navy, however another 18 million litres remain on board, threatening to spill every time a cyclone sweeps by or another tank corrodes through.
The United States Government, who maintain sovereignty over the wreck and its cargo, have off-loaded the remaining fuel to prevent further pollution of the lagoon. The off-loading was completed on 18 March with a total of 1.8 million US Gallons pumped out.
Asia-Pacific ASA (APASA) carried out a detailed oil spill risk assessment to provide planners with an understanding of which environmental resources would be under threat if an uncontrolled oil release occurs. This work was carried out in collaboration with Trevor Gilbert from the Australian Maritime Safety Agency (AMSA) who has been assisting the Pacific Ocean Pollution Prevention Programme (PACPOL).
The study made use of ASA's ocean/coastal hydrodynamic model, HYDROMAP, and three-dimensional oil spill model, SIMAP, to predict the potential and most likely trajectories and fates of oil originating from the wreck.
Contour maps showing the probabilities of exposure by surface slicks, and potential concentrations of physically entrained oil, and dissolved oil components (as aromatichydrocarbons) were some of the outcomes of the study. This information will provide a guide for contingency planning and risk assessment and help the placement of protective equipment to guard sensitive resources and the selection of the optimal timing of operations.
While this study only focused on the risks of exposure from spills associated with the USS Mississinewa, there are another 1800 known WWII wrecks in the South Pacific that are loaded with oils, chemicals and ordnance, which also pose risks to the Pacific environment.
For more information on this study contact
or visit www.seaaustralia.com/wwii_shipwrecks.htm
