OIL SPILL CASE STUDY - Sea Empress
Clean up Mission
A massive clean up operation was launched, both at sea and onshore. The natural beauty of the coastline and its importance for wild life ensured that the clean up operation was extremely efficient and complete. Volunteers helped the conservationists and even the local school children offered their help in the operation.
Most of the bulk oil dispersed naturally (50%), or was chemically dispersed by 460 tonnes of chemical dispersants released from aircraft. The oil degraded by physical, chemical and biological mechanisms. The lighter toxic fractions evaporated from the surface or were removed by photoxidation. The heavier fractions moved into water column and bed sediments or were deposited on beaches and rocky shores. Some oil was recovered mechanically at sea, and between 17 and 25 February 445 tonnes of chemical dispersants were used to break up the oil into disperse droplets in order to reduce the risk to the coastline and to birds at sea. A policy was adopted of not using dispersants within 1 km of the shoreline in order to avoid shallow water (where the dispersed oil would be less readily diluted, thereby increasing the risk to marine life).
Wave-exposed rocky shores improved quickly through natural cleansing, with other rock shores cleaned by spraying with freshwater or scrubbing with straw. The priority in the cleanup was to protect the beaches of high conservation value. Large amounts of oil was removed from beaches using earthmoving equipment, but with some use of dispersants to remove weathered oil from rocks next to selected beaches where amenity value was judged to take priority. Most of the amenity beaches were reopened for Easter. However, many shores were affected by residual oil pollution through the summer of 1996.
The oil spill also gave clean up experts the opportunity to use degrading bacteria and nutrient enrichment in an experimental bioremediation scheme. Of the 73,450 tonnes officially spilled, only 3000 tonnes are estimated to have recovered during the cleanup operation.
Contamination persisted out of sight within shingle, sands and muds and within surviving wildlife. Autumnal storms remobilized buried oil, causing the temporary reappearance of sheens and tar balls on many beaches but these incidents were dealt with rapidly. This storm action accelerated the natural cleansing of the coast. By spring of 1997, few shores showed visible evidence of oiling.
