The Port of Miami Tunnel was conceived as a solution to longstanding traffic bottlenecks in downtown Miami, aiming to provide a direct link between the Port of Miami and major thoroughfares I-395 and I-95. The project broke ground in May 2010 and reached substantial completion on August 3, 2014. As seen in the EarthCam time-lapse video above, the construction process, which spanned several years, involved complex engineering under challenging conditions beneath Biscayne Bay.
Delivered through a public-private partnership between the Florida Department of Transportation and MAT Concessionaire, LLC, the project marked a milestone in Florida infrastructure. It involved the creation of twin tunnels—the first of their kind in the state—using an enormous tunnel boring machine specifically built for this effort. The machine, nicknamed “Harriet,” was engineered to navigate South Florida’s unique subsurface terrain.
The geology posed major challenges, including porous limestone formations and unexpected underground voids. These conditions required the construction team to implement specialized stabilization techniques, including targeted concrete injections, to ensure safe and effective tunneling. In addition to the tunnel itself, the project called for significant improvements to the MacArthur Causeway, which was widened to accommodate the new connections and streamline traffic entering and exiting the port.
Supporting infrastructure was also a critical component, with the development of operational buildings, a dedicated maintenance facility, and improvements to surrounding roadways. The tunnel now serves a vital role in reducing congestion throughout downtown by redirecting port-related truck and cruise traffic away from surface streets. In doing so, it has not only enhanced urban mobility but also strengthened the Port of Miami’s logistical efficiency and economic impact on Miami-Dade County.