Dolly

On 5 November 1999, the bitumen carrier Dolly, transporting 200 tonnes of bitumen, tore its hull on the reef and sank 25 m deep into the lagoon, as it had missed Robert’s pass. Hydrocarbon iridescences, coming from the engine room, were observed at the surface that day and the following day. The cargo did not generate any risks of short-term pollution, as the bitumen tanks had not been pierced. Bitumen, the final part of the refining process, is insoluble in water and its density is generally higher than water’s at a softening point between 3°C and 70°C. The relative solidification of the cargo contained in the tanks seemed the most likely scenario at the time, until the tanks would rip open in a storm, after years of rusting.

The French West Indies Navy command decided to remove from the wreck the only fluid which could prove to be a risk for the environment: the 3.2 m³ of diesel oil held in the ship’s bunker. Several options were considered, such as the use of submerged diaphragm pumps, tank depression pumping with a cesspit emptier, freeing the diesel and recovering it at the surface by confining it with an antipollution boom (the technique used for the Peter Sif by Ushant island). This last solution was ruled out because the current in this zone, estimated between one and three knots, was always higher than the efficiency limit of the anchored booms. At the end of the year it was decided that a pumping operation would be undertaken at the beginning of the year 2000.