Massive Machine Built to Drill Port of Miami Tunnel

Miami traffic can be crazy, especially on the MacArthur (5^th Street) Causeway that connects Downtown to South Beach. The locals commuting to and from work and school, combined with the tourists in taxis and rental cars that come and go daily, and on top of that the trucks heading to the Port to drop and pick up shipments. This combination of traffic often causes a real jam.

Nearly 16,000 vehicles travel to and from the Port of Miami (POM) through downtown streets each weekday. Truck traffic makes up 28% (or 4,480) of this number. In order to keep the roads safe and less congested the City of Miami decided to widen MacArthur Causeway and build a tunnel to provide a direct connection from the Port of Miami to highways via Watson Island to I-395 and I-95 to create another entry to the Port of Miami besides the Port Bridge. The POMT will improve traffic flow in downtown Miami by reducing the number of cargo trucks and cruise related vehicles on congested downtown streets.

The Project includes a tunnel under Government Cut, roadway work on Dodge and Watson Islands, and MacArthur Causeway Bridge widening. The rebuilding of the bridge and roadways at the Port of Miami, located on Dodge Island began in December 2010 and the tunnel is expected to be opened to the public by May 2014. The total cost of design and construction of the tunnel is set at $607 million.

A special machine had to be created just to complete this project. A 43-foot diameter Tunnel Boring Machine (TBM) was specifically constructed for the project in Germany. It is the length of two football fields, the largest machine in the U.S. working in soft ground conditions.

The TBM arrived in Miami in pieces and had to be assembled. The tunnel contractors lowered the 530,000-pound cutting head from the surface into the 50-foot pit where the machine is being put together.  Digging about four feet an hour, the TBM, nicknamed ‘Harriet’, will take six months to re-emerge at the port on Dodge Island.  The huge cutter head for the machine was lowered into the pit Thursday, September 1, where the new tunnel access road to the Port of Miami will start on Watson Island.

The machine will generate millions of tons of pressure as it grinds through the soft limestone rock under Government Cut. As the cutting head rotates, Harriet will inject grouting into the porous limestone to seal it. A crane installed between the engine section and the gantry will then put into place the 12-ton panels of incredibly smooth, curved cast concrete that will form the walls of the tunnel.

Once ‘Harriet’ is finished with the tunnel her time on earth is done. TBMs are not reusable since they are designed for the specific parameters and conditions of each project. If you happen to be in the area today drive by to catch a glimpse of Harriet before she goes underground for 6 months.

Click here for more information on Harriet and the Port of Miami Tunnel Project.