- Jakob Maersk
- Accident date
- Accident area
- Entrance to Leixoes harbour, Porto (Portugal)
- Spill area
- Cause of spill
- Quantity transported
- 80,000 tonnes iranian heavy crude oil + 4,000 tonnes heavy fuel (Bunker C)
- Nature of pollutant
- Iranian crude oil + heavy fuel oil (Bunker C)
- Quantity spilled
- 84, 000 tonnes
- Ship / structure type
- Oil tanker
- Built date
On 29 January 1975 at 12:30 pm, the oil tanker Jakob Maersk hit a sandbank while trying to enter the harbour. A few seconds later, there was an explosion in the engine room. The oil tanker caught fire and broke into three parts. The central and the stern parts sank while the bow part remained afloat. It ran aground on the beach a few days later. The explosions destroyed all the main tanks of the oil tanker and significant quantities of crude oil leaked from the wreck. A certain amount was partially burnt by the fire, another part of the oil was dispersed at sea or washed up on the coast.
On the days when the fire was at its worst, the flames were 100 metres high. The sky above Porto was darkened by a thick black smoke for several days. 7 out of the 17 crew members died during the disaster, as most of them were in the engine room during the explosion. Several inhabitants living in this area were sent to hospital because of the smoke.
A follow-up operation was set up with aerial suveillance patrols. The explosions and the fire raged on the wreck for the two first days, preventing any oil recovery attempt at sea. Collaboration between the Ministry of fisheries, the Army, the Navy, the ship owners, Shell and a large part of the local population allowed rapid action to be taken to limit the damage. A floating boom was installed in the harbour entrance to prevent oil slicks from entering the harbour. A straw barrier surrounding the wreck retained the oil sufficiently until boats had spread dispersants. The most affected beach was the shore immediately adjacent to the Jakob Maersk.
Clean-up operations began with the removal of the upper sand layer. Dispersants were also spread on the sand. Wave action facilitated the elimination of oil from the rocks. It was estimated that the fire around the ship burned between 40,000 and 50,000 tonnes of oil, that 25,000 tonnes drifted at sea and nearly 15,000 tonnes were washed up on the beach. Hydrocarbon traces were found on beaches situated 50 km from the wreck.
The majority of the ecological damage was observed on the foreshore. In rocky areas, seaweed (Fucus sp.) and molluscs (mussels) were found dead. But growth was resumed a few months later and mussels populations recovered from the accident. No harmful effect was observed on fish populations but the taste of fishery products was altered temporarily. Very few birds were affected, at least in the coastal zone. In the course of the first week, only half a dozen oiled birds were found in north Porto.
The cost of the catastrophe was estimated at 2.8 million dollars by OECD (Organisation for Economic Co-operation and Development).