Monday, September 16, 2013

Pearl Harbor and the Costa Concordia salvage operation


I'm sure most people aren't aware of it, but there's a link between the attack on Pearl Harbor in 1941 and the salvage of the Costa Concordia cruise liner currently in progress.

The salvors are using a technique known as parbuckling or parbuckle salvage, where lines are fastened to and around a ship and used to haul her upright.  Prior to the current operation, the largest ship recovered from the seabed using this technique was the battleship USS Oklahoma, sunk at Pearl Harbor.  She was righted in 1943 using the parbuckling technique (shown below).




Compare the parbuckling cables above (leading to winches ashore) to those attached to the Costa Concordia, below, which lead to a steel framework sunk into the seabed, and from there to tugs and winches to pull her upright.




Here's a series of pictures of salvage work on USS Oklahoma and USS Utah at Pearl Harbor during World War II.  I recommend watching it in full-screen mode.  After the former was hauled upright, cofferdams were built around her to permit repairs to be made to her hull, restoring her watertight integrity.  Refloated, she was taken into dry dock.  Parbuckling was also attempted on the latter vessel, but failed when the ship slid along the seabed rather than turn upright.  She was abandoned in place, and still lies there.  The music is the Washington Post March by John Philip Sousa.





More photographs of the salvage of USS Oklahoma may be found here.

The end of USS Oklahoma was both dramatic and very dangerous.  Wikipedia reports:

In May 1947, a two-tug towing operation began to move the hull of the Oklahoma from Pearl Harbor to the scrapyard in San Francisco Bay. However, disaster struck on 17 May when the ships entered a storm more than 500 miles from Hawaii. The tug Hercules put her searchlight on the former battleship, revealing that she had begun listing heavily. After radioing the naval base at Pearl Harbor, both tugs were instructed to turn around and head back to port. But suddenly, without warning, the Hercules was pulled back past the Monarch, which was being dragged backwards at 15 knots herself. The Oklahoma had began to sink straight down causing water to swamp the sterns of both tugs.

Fortuitously both tug skippers, Kelly Sprague of the Hercules and George Anderson of the Monarch, had loosened their cable drums which connected the 1,400 feet tow lines to the Oklahoma. As the battleship rapidly sank, the line from the Monarch quickly played out releasing the tug. However the Hercules' cables didn't release until the last possible moment, leaving her tossing and pitching above the grave of the sunken Oklahoma.

I imagine that must have been a pretty scary experience for the crews of the tugs!

Here's a video report about a veteran of USS Oklahoma and his recollections of her sinking.





May all who died aboard her, and the other ships targeted at Pearl Harbor, rest in peace:  and may the same grace be granted to the dead of the Costa Concordia.

Peter

EDITED TO ADD:  This video clip shows a time-lapse portrayal of the righting of the Costa Concordia.  From about the 1m.5sec. mark, you can see a series of shots of the ship upright in the water, including some focusing on her starboard side, which has been underwater and pressed against a rocky outcrop since she sank.  You can see how the massive weight of the ship, pressing down on the rock, has actually conformed her outer hull to the shape of the seabed.  That demonstrates what a difficult job this salvage has been (and will continue to be).




2 comments:

  1. Yep, what's old is new again, and the Oklahoma's story is a sad one.

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  2. Ahh, so that explains why they early on decided that it wasn't worth doing a refurb. I didn't know it had crushed the down side on rocks like that. I just figured they were looking at the bad PR from trying to reintroduce it after killing a batch of people.

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