The project involves building the new 2.4 mile two-tube Gateway Tunnel under the Hudson River and refurbishing Amtrak’s existing 112-year-old North River rail tunnel, which was badly damaged by Hurricane Sandy in 2012. Amtrak’s Northeast Corridor is the most heavily-used passenger rail line in the US.

In addition to the rising cost, the start of construction has been pushed back more than a year to autumn 2024. The completion date has been delayed by three years so the new tunnels should be in operation by 2035 and the tunnel refurbishment completed by 2038.

The Gateway Development Commission, the bi-state public authority charged with overseeing the Gateway Program to upgrade train infrastructure between the two states, attributed the increased price tag to inflationary costs and supply chain issues.