Workers start on twin roadways through PortMiami tunnel

The $1 billion under-the-bay tunnel to PortMiami has reached another milestone on its way to its spring 2014 completion date.

Inside the tunnel tubes already excavated under Biscayne Bay, workers have begun building the twin roadways that will carry cargo trucks, tourist buses and private cars from the MacArthur Causeway to the port and back.

The massive entry and exit portals also are under construction for the tunnel that is expected to be mostly completed by May.

On Tuesday, hundreds of workers were putting the finishing touches on what will be the first direct road connection between the port and area expressways.

Currently, trucks, buses and private vehicles from the port must meander through congested downtown streets to reach Interstate 95 and State Road 836 (the Dolphin Expressway).

Once the tunnel is open, traffic will be able to reach I-95 and 836 via the MacArthur Causeway — which links up with Interstate 395, a spur leading to both expressways.

“By the end of May, we will have substantially completed the only tunnel going to a port in the United States from a major interstate,” said Chris Hodgkins, vice president of Miami Access Tunnel, the multinational firm building the facility. The tunnel will run to the cargo area and cruise terminal area without traffic signals, Hodgkins said.

This portion of the project started in November 2011 when a giant tunnel boring machine began digging the eastbound tunnel tube from the median of the MacArthur Causeway at Watson Island to the port.

In July 2012, it turned around and began boring the westbound tube back to Watson Island. The machine, dubbed Harriet, popped up above the surface at Watson Island in May 2013.

The twin tubes originally resembled holes in the ground with dirt paths sloping downward from the surface to a point 120 feet beneath Biscayne Bay. As Harriet pushed its way underground, slicing through rock, it installed concrete panels on the bare oval walls of each tunnel.

On Tuesday, the facility resembled a massive tunnel with twin tubes whose entrances and exits are marked by huge stone portals designed by famed Miami architectural firm Arquitectonica.

The portals, at Watson Island and the port, house huge metal gates that will seal the tunnel to prevent flooding in case a massive hurricane approaches.

“So when the Coast Guard gives a notification of a Category Three [storm], two 50-ton metal gates come down and seal the tunnel, water-tight,” Hodgkins said. “There won’t be any water that will be getting into the tunnel.”

At the approach to the Watson Island portal, a team worked on an artistic wall lining the tunnel entrance. The engraved wall is designed to resemble sea grass.

The dirt paths inside the tubes are being prepped for the two-lane roads that will carry traffic. Over the next 60 days, workers will add layers of concrete and asphalt to finish the twin underground highways.

The concrete walls inside the tubes are now acquiring elegant touches in black and white as workers install 200 miles or internal wiring and fireboard. Later, ceramic panels will go over the fireboard, Hodgkins said.

Teams are working around the clock to complete the facility on schedule, Hodgkins said.

The tunnel is part of a major overhaul of PortMiami designed to turn the marine terminal into a major cargo hub once the expanded Panama Canal is completed in 2015.