MV Tricolor, a 55,000-ton Norwegian-flagged vehicle freighter, sank in the English Channel in 2002 carrying 2,871 Volvos, Saabs, and BMWs worth $100 million. How do you salvage a boat that big? Start with a really big band saw.
In the wee hours of December 14, 2002 the MV Tricolor collided with another boat, the Kariba, and while the Kariba was able to travel on to port, the MV Tricolor sank on the edge of a busy shipping lane — just below the surface in 98 feet of water. Over the next two weeks the wreckage was struck by no fewer than three ships despite buoys and police guarding the site. With the wreckage sitting in such a busy lane it had to be removed.
Starting in 2003, Smit International of the Netherlands began a thoroughly amazing salvage operation. Small wrecks can normally be hoisted from the bottom of the sea using a variety of methods, but because the MV Tricolor was so heavy it needed to be sliced up while on the bottom of the channel so its pieces could be lifted. How do you cut up something that's in 98 feet of water? The process uses a pair of self-jacking stationary rigs and a very sturdy cutting wire.
Using side-scanning sonar and GPS positioning data, the team created a three dimensional map of the crashed freighter and planned eight cuts for a total of nine sections each weighing between four thousand and six thousand tons, each easily lifted by sea cranes. Using the data, the two stationary rigs were placed on either side of the wreckage and and lifted above sea level. The cable which is coated in a material called WIDIA and comparable in hardness to diamonds, was routed from one rig right under the wreck and over to the other rig. Using power winches and gradually tightening the line, the cable acted like a giant saw, moving back and forth and slowly sliced through the ship, bottom to top. Everything inside got the same treatment, from the engine room to the doomed cars in the cargo hold.
The huge pieces were lifted from the bottom and placed on a float barge for transport to Zeebrugge harbor for metal salvage. When the large pieces were gone, teams with grab cranes moved in, cleaning up the remaining bits and whatever cars had fallen out during the process.
In all, the full recovery was completed in approximately a year. All the vehicles were scrapped and the loss totaled somewhere in the neighborhood of $100M USD at the time of the accident. At least as a consolation we get amazing pictures of a ship and its load of cars sliced open.