MIAMI -

Drivers on the MacArthur Causeway may have noticed some new construction popping up, thanks to the Port of Miami Tunnel project.

The new catwalk-like overpass above the causeway is about to become a dirt highway, as trucks use the overpass to carry tons of fill unearthed by the giant tunnel boring machine.

The machine, nicknamed "Harriet," is set to start whirling next month, unearthing some 400,000 cubic yards of dirt, silt, soil and rock.

The Port of Miami Tunnel is being dug under Government Cut.

The 600 feet long and 12 feet wide conveyor will move the spoils as they emerge from the tunnel construction site. The trucks will then travel along the causeway median and up and over the causeway to a collection pit on the Watson Island side.

An estimated six trucks an hour will fill up and haul away the fill. Most of the fill is headed to Virginia Key to cap the landfill, and to build a bank around the sewage plant there.

The tunnel boring machine will be publicly debuted Friday, Nov. 4.