A massive tunnel-boring operation for the new Gateway rail tunnels beneath the Hudson River is officially getting underway, marking the first construction of a new rail tunnel under the river in more than a century.

Officials gathered Monday in North Bergen, New Jersey, to launch the first of two giant tunnel-boring machines that will carve out the initial section of the new rail connection between New Jersey and Manhattan.

The $16 billion Hudson Tunnel Project is designed to increase capacity and improve reliability along the heavily traveled rail corridor into Penn Station. The current North River Tunnel, which dates back to 1910 and was badly damaged by Hurricane Sandy, carries nearly 200,000 passengers each day.

The enormous machines feature cutterheads nearly 29 feet in diameter and trailing equipment stretching about 500 feet. They will first travel roughly 5,100 feet through the hard rock of the New Jersey Palisades, advancing approximately 30 feet per day. Once that section is completed, the machines will be replaced with equipment specifically designed to tunnel beneath the Hudson River.

Final testing is expected to wrap up shortly, with the first machine beginning excavation in the coming days. A second machine will follow soon after. The new tunnels are currently expected to open in 2035, after which the existing tunnels can undergo major rehabilitation.

The project is being funded by federal, New York and New Jersey contributions and has faced multiple funding disputes and legal battles. Construction has since resumed, with the Gateway Development Commission continuing work on the project.