successful salvage of the remainder, have been identified in the last thirty years or so, although tankers often are lightened for refloating.
The only purposeful jettison of oil cargo identified in recent years was from the Zoe Colocotronis. After grounding off Puerto Rico in 1973, some 5,000 tons of crude oil were jettisoned and the ship was refloated. The case is notorious, Ellis said, because such drastic action now appears to have been unnecessary. When the Arrow grounded off Nova Scotia in 1970, jettisoning was authorized, but part of the vessel sank before action could be taken. After the Argo Merchant ran aground on Nantucket Shoals in 1976, jettisoning was suggested but rejected. The vessel eventually was lost.
According to Ellis, salvors are reluctant to jettison even when it may be more expedient than waiting for proper equipment and weather to lighten the ship. He cited three reasons:
Salvors are concerned about the environment and want official approval to jettison.
Discharge of valuable oil cargo means a reduction in the salved values and perhaps in the salvage award.
Circumstances of groundings rarely support a clear-cut decision to jettison.
Nonetheless, in cases where tugs cannot refloat a tanker and lightering is not possible, it may be "better to jettison and accept that sometimes sacrifice is necessary for the common good," Ellis said.
F.R. Engelhardt, vice president for research and development for the Marine Spill Response Corporation, discussed environmental risk as a function of oil spill size. Variables that can influence risk include characteristics of the oil, physical environmental conditions, containment and recovery measures, geology of the impact zones, toxicological sensitivity of vulnerable species, and ecological characteristics of vulnerable areas. These variables interact to drive weathering rates and persistence, spread of the spill, direction of slick movement, effectiveness of response measures, size of the impact zone, extent and duration of biological effect, and degree and rate of recovery. Thus, large spills do not necessarily have greater potential for environmental impact than do smaller spills. Engelhardt said the spill size influence should be analyzed in depth based on the global record for marine spills, perhaps using a proposed marine oil spill scale similar to the Richter scale for earthquakes.
Jerry Galt, a physical oceanographer at the National Oceanic and Atmospheric Administration (NOAA), described oil spill trajectory modeling. He outlined how these models work, the types of models available, factors that limit model accuracy, how models are used, the technology available to support models, and needed improvements. Models can be used to estimate some aspects of currents and the projected distribution of jettisoned oil. Models are not a tool for arriving at a definitive recommendation to jettison, Galt said, but they can establish that a situation will deteriorate if such action is not taken. "It is an exploration of the situation—to find out the worst downside and then plan for that scenario," Galt said.
Warren L. Dean and Laurie L. Crick, a senior partner and an associate, respectively, in the law firm of Dyer, Ellis, Joseph & Mills, summarized laws affecting the jettisoning of oil. Under current laws, a salvor does not qualify for any award unless some property is saved—thus the "no cure, no pay" principle traditionally