The new tunnel and related highway improvements reroute port traffic along Interstate 395 over the MacArthur Causeway Bridge to Watson Island, and then through the 3/4-mile-long, twin-bore tunnel under Biscayne Bay to Dodge Island and the port. Trucks and cruise passengers, including travelers en route to and from Miami International Airport, can now bypass downtown streets entirely.
To accommodate the increased traffic volume, the MacArthur Causeway Bridge was widened to eight lanes (four in each direction), and the causeway itself – a major interstate highway – was relocated along with other local roads to make room for the tunnel entrance on Watson Island.
The scope of the project also included construction of two operational buildings and a maintenance facility, roadway access improvements for tunnel traffic, bridge and road improvements on Dodge Island (including construction of 1,200 feet of additional railroad track), extensive utility relocation work, construction of deep wells for drainage, lighting for Watson and Dodge islands, traffic signals, signage, and pavement markings.
The PortMiami Tunnel is the first bored roadway tunnel ever constructed in South Florida’s complex sedimentary geology. To date, it is the largest-diameter bored soft ground completed tunnel in the U.S.
The project team overcame significant challenges, including a major grouting problem beneath Biscayne Bay, construction in a coastal, hurricane-prone environment; design requirements to resist 500-year storm events; and restrictions that construction could not interfere with cruise and cargo traffic or the native manatee or corals in Biscayne Bay, which is a state-designated aquatic preserve.