Case Histories - A

ABT SUMMER (Off Angola, 1991)

On 28th May 1991, while en route from the Gulf terminal at Kharg Island, Iran to Rotterdam the tanker ABT SUMMER, fully laden with a cargo of 260,000 tonnes of Iranian heavy crude oil, experienced an explosion and a fire about 900 miles off the coast of Angola. Five of the 32 crew members on board died as a result of the incident.

A large slick covering an area of 80 square miles spread around the tanker and burnt fiercely. The ship burned for three days before it sank on 1st June and subsequent efforts to locate the wreckage were unsuccessful.

It is not clear how much of the oil sank or burned. However, as the incident occurred very far off-shore, most of the oil was expected to be broken up by high seas with little or no environmental impact.

Selected Bibliography

Hooke, N. (1997) Maritime casualties, 1963-1996.  2nd edition, LLP Limited, London

Oil Spill Intelligence Report, 30 May 1991 & 6 June 1991

 

AMOCO CADIZ (France, 1978)

AMOCO CADIZThe tanker AMOCO CADIZ ran aground off the coast of Brittany on 16 March 1978 following a steering gear failure. Over a period of two weeks the entire cargo of 223,000 tonnes of light Iranian and Arabian crude oil and 4,000 tonnes of bunker fuel was released into heavy seas. Much of the oil quickly formed a viscous water-in-oil emulsion, increasing the volume of pollutant by up to five times. By the end of April oil and emulsion had contaminated 320km of the Brittany coastline, and had extended as far east as the Channel Islands.

Strong winds and heavy seas prevented an effective offshore recovery operation. All told, less than 3,000 tonnes of dispersants were used. Some chalk was also used as a sinking agent, but with the consequence of transferring part of the problem to the sea bed. The at-sea response did little to reduce shoreline oiling. A wide variety of shore types were affected, including sandy beaches, cobble and shingle shores, rocks, seawalls and jetties, mudflats and saltmarshes. Removal of bulk free oil trapped against the shore using skimmers proved difficult, largely due to problems with seaweed and debris mixed with the oil. Greater success was achieved with vacuum trucks and agricultural vacuum units, although much of the free oil was simply removed by hand by more than 7,000 personnel (mainly military). A considerable portion of the oil that did come ashore eventually became buried in sediments and entrapped in the low energy salt marshes and estuaries.

At the time, the AMOCO CADIZ incident resulted in the largest loss of marine life ever recorded after an oil spill. Two weeks after the accident, millions of dead molluscs, sea urchins and other benthic species washed ashore. Although echinoderm and small crustacean populations almost completely disappeared from some areas, populations of many species had recovered within a year. Diving birds constituted the majority of the nearly 20,000 dead birds that were recovered. Oyster cultivation in the estuaries ("Abers") was seriously affected and an estimated 9,000 tonnes were destroyed because of contamination and to safeguard market confidence. Other shell and fin fisheries as well as seaweed gathering were seriously affected in the short-term, as was tourism. Cleanup activities on rocky shores, such as pressure-washing, as well as trampling and sediment removal on salt marshes caused biological impacts. Whilst rocky shores recovered relatively quickly, the salt marshes took many years. Failure to remove oil from temporary oil collection pits on some soft sediment shorelines before inundation by the incoming tide also resulted in longer-term contamination. Numerous cleanup and impact lessons were learned from the AMOCO CADIZ incident, and it still remains one of the most comprehensively studied oil spills in history.

Selected Bibliography

Bellier, P. and Massart, G. (1979). The Amoco Cadiz oil spill cleanup operations - an overview of the organisation, control and evaluation of the cleanup techniques employed. Proceedings of the 1979 Oil Spill Conference, 141-146. API Publication No. 4308. American Petroleum Institute, Washington, DC, USA

NOAA (1978). The Amoco Cadiz oil spill: A preliminary scientific report. A National Oceanic and Atmospheric Administration and Environmental Protection Agency special report, Washington DC, USA

Spooner, M.F. (editor) (1978). The Amoco Cadiz oil spill. Special edition of Marine Pollution Bulletin 9 (7). Pergamon Press, Oxford and New York

Conan, G., d'Ozouville, L., and Marchand, M. (1978). Amoco Cadiz - preliminary observations of the oil spill impact on the marine environment. One day session, Amoco Cadiz, Brest, France, 7 June 1978. Le Centre National pour l'Exploitation des Oceans, Paris, France

Links

CEDRE - Case History
www.cedre.fr

 

ARGO MERCHANT (USA, 1976)

ARGO MERCHANT ran aground on Nantucket Shoals, off Massachusetts, USA, on 15 December 1976, and over the next month spilled her entire cargo (28,000 tonnes) of Venezuelan No 6 fuel oil and cutter stock. Storms broke up the tanker after grounding, and attempts to pump the oil into another vessel failed. In-situ burning was attempted on two occasions, but the slick failed to remain alight.

Winds during the spill period were offshore from Massachusetts, and as a result no oil from ARGO MERCHANT ever reached the shoreline and no coastal impact was reported. Hydrocarbon contamination of the bottom sediments was restricted to an area immediately around the wreck, and apparently was short-lived. The bulk of the spill formed large 'pancakes' and sheens on the surface; these were carried offshore over the continental shelf and into the prevailing North Atlantic circulation pattern. The cutter stock, which was mixed with the fuel oil to improve handling, entered the water column. Despite its relatively high potential toxicity, there was little evidence of impact on the marine fauna or phytoplankton. The accident occurred at the time when the fewest potential effects on pelagic organisms would be expected; a period of low productivity in the water column, with few fish eggs and larvae present. Oiled birds were seen near the wreck, and though total mortalities are difficult to evaluate, it was concluded that the spill probably had little effect on the coastal and marine bird populations off the New England coast. The outcome of the ARGO MERCHANT oil spill appears to have been fortunate in several respects: - the winds were almost continuously offshore, preventing the oil from coming on the beaches; the density of the oil was low enough so that it did not sink and contaminate the bottom, and the spill occurred in the winter when the biological activity, productivity, and fishing activities are relatively low.

Selected Bibliography

Winslow, R. (1978). Hard aground: The story of the Argo Merchant oil spill. W.W. Norton & Company Inc, New York, USA

Grose, P.L. & Mattson, J.S. (editors) (1977). The Argo Merchant oil spill: A preliminary scientific report. Govt Print. Off. [for] Department of Commerce, National Oceanic and Atmospheric Administration, Washington, DC, USA

Center for Ocean Management Studies (1978). In the wake of the Argo Merchant. Proceedings of a Symposium, 11-13 January 1978. University of Rhode Island, USA

Return to top

« Back to Case Histories Index