Boskalis_Annual Report_2017

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ACTION PLAN The Greek authorities then issued a tender for the removal of the stern from the sea floor. The stern weighed approximately 1,450 tons and it included machine and engine parts, as well as the accommodation for the crew. “The immediate reason for the wreck removal was to prevent environmental damage,” explains Van der Jagt. “In addition, the government wanted to make sure that parts of the accommodation, including personal belongings, wouldn’t escape from the stern in time.” Various additional bathymetric surveys were conducted so that the Salvage team had a clear picture of the local conditions. That allowed them to submit a detailed plan of action for the wreck removal, which was conducted in the fall of 2017 following the contract award earlier that year. “An important factor was that we knew we could use the Taklift 4, a Boskalis floating sheerleg crane, that was working at another place in the Mediterranean,” says Van der Jagt. “The fact that we can use the expertise and the versatile Boskalis fleet worldwide is an advantage on salvage projects. Of course, on projects like this, we try to use our own equipment as much as possible.” CONTROLLED LIFTING “With a lifting capacity of 2,200 tons, the Taklift 4 was ideal for this wreck removal,” continues Van der Jagt. “The Taklift 4 is also equipped with four lifting blocks and that factor above all was crucial for the approach we adopted. It meant we could complete the lifting operation very precisely and in a controlled manner.” The stern was listing on the sea floor at an angle of about 25 degrees. For safety reasons, the team wanted to keep the wreck at the same angle and raise it onto a barge. “After we had positioned the lifting chains under the wreck, we were able to use the lifting blocks to adjust the strain on the lifting chains precisely. As a result, the operation went exactly according to plan,” says Van der Jagt. ENVIRONMENTAL BARRIER Prior to the lifting operation, the team ftted out the barge with an environmental barrier, a large steel container welded onto the deck of the barge. “We had already removed the fuel from the wreck,” says Van der Jagt, “but if you place such a huge stern in its entirety on a barge, there is always a risk of pollutants being spilled. The environmental barrier made sure that those substances didn’t pollute the seawater.” The stern was positioned precisely on a layer of cribbing wood which was installed frst to protect the deck. The barge was then ballasted. “After we had seafastened the wreck, we towed the barge to a nearby yard where the stern will be recycled in a controlled manner,” concludes Van der Jagt.

The Taklift 4 removing the stern of the Cabrera from the seabed in Greece.