Oil removal
TotalFinaElf committed to neutralising the danger represented by the oil (bunkers and cargo) trapped in the wreck of the Erika, under the control of the French Government. A survey showed that pumping offered the best advantages, particularly in terms of safety and environmental protection when implemented.
Once pumping had been chosen as the best solution, various technical options were proposed by companies specialising in underwater response. The technique selected by TotalFina was validated by the Government's steering committee and group of experts. It consisted in drawing off the hydrocarbons based on the difference in hydrostatic pressure between the wreck and an intermediate tank lying on the seabed and maintained in controlled relative depression. In order to facilitate its transfer, the oil was fluxed by mixing with a thinner (rapeseed methyl ester), harmless for the environment, as soon as it flowed out of the wreck and before reaching the intermediate tank. Once it was in the tank, the oil-thinner mixture was sent towards the surface in a continuous flow using a double-screw pump. A phase of fine cleaning of the wreck, comprising the elimination of as much as possible of the residual oil remaining after pumping, was planned by injecting rapeseed methyl ester.
Various subsea intervention companies put forward bids to Totalfina. After studying the different proposals, the French-Norwegian consortium Coflexip/Stena Offshore/Stolt Offshore was was selected to carry out the operations. The preparation of the two parts of the wreck, 10 km apart, began in mid-May by a survey phase and by the contractors setting up the work site. Hull drilling and the installation of the connecting systems to the pumping device started at the beginning of June. This was carried out by remote-controlled robots (ROV) and by divers who worked more particularly on the areas that were difficult to access. This phase started with the bow before beginning on the stern, which was more complex because of the obstruction of the deck. A little over 10,000 tonnes of heavy fuel oil were recovered during the main pumping operations. Fine cleaning added a further 1,200 tonnes.