Once the TBM has completed both tunnels, most parts from the trailing gear (gantries) will be sold back to Herrenknecht, the manufacturer, for reusing in other TBMs. The other parts that cannot be resold, such as the shield and cutter-heard, will be recycled.
A tunnel boring machine (TBM) is used to dig tunnels. It consists of a cutter head and trailing gear that carries support equipment and moves excavated material out of the tunnel. The Port of Miami Tunnel project will use a TBM built specifically to work in the geological conditions of Government Cut and dig the two tunnels.
The total length of the TBM is 428.5-feet long (more than one football field), consisting of a 361 foot long trailing support gear made up of 6 gantries and a cutter head with an outside diameter of 42.3 feet (as high as a 4 story building).
TBMs are a very specialized type of equipment and only a few companies in the world build them. The Port of Miami Tunnel TBM was built by Herrencknecht. Once completed, the machine was tested, disassembled and then shipped in pieces to the Port of Miami.
Once unloaded from the ships, the TBM was moved to Watson Island. It was put back together in the median of the MacArthur Causeway, where the contractor dug a hole, or pit. The machine began excavating there.
The TBM began mining the first tunnel on November 11, 2011 and the TBM broke out on Dodge Island (PortMiami) on July 31, 2012. The machine was then partially disassembled, turned around and reassembled and began mining in the Westbound direction towards Watson Island on October 29, 2012. Completion of the second tunnel was completed on May 6, 2013.