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continued from page 8
         meant that the towers need to be located
         at the other end of the bridge. In order
         to accomplish that, engineers came up
         with the idea of building a tunnel on the
         Denmark side of the straits. That tun-
         nel actually had to start on an artificial
         island to be built out in the Straits.
           The decision was made to build an is-
         land from scratch. When completed, the
         existence of the island meant Denmark
         had increased in size by 1.3 million
         square meters. Four kilometers of road
         on the artificial island and four in the
         tunnel left another eight miles of water
         to be covered. To figure out what type
         of bridge may be used for the rest of the
         distance, a design competition was held.
           One design which  proved appealing
         was that of an arch  bridge. But such
         structures eventually diminish all the
         way to zero in the space between the
         water on the bridge span, space need-
         ed for vessels to pass underneath the
         structure.  A suspension  bridge would
         have  been  possible,  however,  such
         bridges also have a lot of up and down
         movement depending upon how much
         traffic is on the deck. This bridge fea-
         tured cars and trains. There would be
         the danger of train derailment due to
         oscillations on the bridge.
           The best option proved to be a cable-
         stay bridge – with the added benefit of
         the  structure  actually being  less  ex-
         pensive; the two main cables of a sus-
         pension  bridge require  much  more
         steel in construction. So the push was
         on to complete the bridge in five years
         because that was when the treaty be-  On August 14, 1999 when this photo was taken and the Øresund Bridge was complete, Danish
         tween the two countries expired.   Crown Prine Fredrik came from Denmark's side and Swedish Crown princess Victoria came from
           The first thing needing to be done was   Sweden side and both ceremoniously met in the middle. Photo © Francis Dean |
         the man made island – built in just 14
         months. On the 17th of August, 1995   Baltic Sea were not deep enough for it.   and waste through a four km-long pipe.
         work started. Large quarried stones   Digging, dredging, and then transport-  Though plumes of debris threatened the
         were brought in from Sweden, with a   ing the material had to take place.  environment, in the end the underwater
         1.8 billion kg perimeter of stone fill com-  An armada of 50 vessels assembled to   clouds resulting were no more than 5%
         pleted  first.  To  remain  on  schedule,  16   navigate in strong currents and some   debris. One unexpected hazard was the
         barges dumped 80 million kg of fill rocs   very shallow water, the tunnel sections   discovery of a 36 kg bomb dredged up
         per day. Each load was carefully placed   which were 11 meters deep and 46 me-  during construction. Luckily the bomb
         using GPS to create the perimeter which   ters wide. A total of 2 million meters of   was able to be defused by bomb experts;
         was in turned filled in with enough ma-  seabed had to be excavated. Ninety per-  disaster was narrowly escaped.
         terial to build a new island 12 km long.   cent of what they had to excavate was   However more World War II bombs
         The fill took millions of cubic meters of   a rock material known as Copenhagen   soon  were  discovered  through  bomb
         material, dredged from the sea bottom.   limestone; even the Chicago could not   sweeps,  some  16 were  discovered,  re-
           Phase Two was involved with the   make a dent in this seabed layer.  moved, and safely destroyed. Troubling
         dredging – something of a win-win situ-  A special mega drill bit, a spinning cut-  as well was the more pragmatic issue
         ation  as  the  daily  11.3  million  cubic   ter, suction dredger – called the Casta   of basic differences in how each country
         meters came from the area being exca-  – had some 60 cutting blades. Another   was set up.
         vated for the bridge tunnel. This work   name for this tool is the “spinning cone of   Something akin to a computerized
         required the most powerful dredger in   death.” Despite the grim name, the lime-  Rosetta Stone had to be created to deal
         the world, The Chicago. The bucket is   stone just below the surface of the water   with  voltage differences  between  the
         large enough to hold a minivan – some   still destroyed some 52,000 teeth as the   two country and in turn the powering
         22 cubic meters of seabed moved in one   dredger worked to both cut through the   of the rail trains soon to be spanning
         scoop. The floating platform to hold this   rock and vacuum out debris.   the Straits. Each country also had dif-
         equipment was so large that parts of the   Giant pumps then forces the water           continued on page 12

         10     Wire Rope News & Sling Technology   April 2017
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