Boehlen

On 15 October 1976, an East German oil tanker, Boehlen, transporting 9,500 tonnes of "Boscan", a type of Venezuelan heavy crude oil, heading towards Rostock (Germany), was caught in a violent storm and sank off the coast of Sein island. The majority of the oil, which had been heated to 40-45 °C to facilitate pumping when unloaded, leaked from the tanks. The Polmar plan was triggered. The vast oil slicks hit the shores of Sein Island, before reaching the Breton coastline, where they threatened the local fauna (fish, molluscs and crustaceans).

On the coastline, the army collected 1,000 tonnes of Boscan, mixed with 7,000 tonnes of various residues, using buckets and shovels.

At sea, the Polmar authorities first tried to plug the leaks of the wreck by filling them with concrete. Then in February 1977, due to pressure from local fishermen and the tourist industry, the French Government decided to pump out the 2,500 tonnes of crude oil left in the tanks. The method, established by the French Oil Institute (IFP), involved pumping the oil out using seawater heated to 80°C. The operation was implemented using the Petrel, a French dynamic positioning drill ship. It began in May 1977 and finished at the end of August 1977. The crude oil collected at sea was burnt using a flare.

25 of the 32 crew members lost their lives in this accident, as well as two divers, during the pumping operation. One soldier, involved in the onshore clean-up operation, was swept out to sea by a large swell.