It’s widely regarded as among the most vital infrastructure projects in the U.S., but it’s been canceled once and now is stuck in limbo. President Donald Trump’s administration ranks the tunnel near the bottom of 37 rated projects vying for federal mass-transit grants and loans. Proponents of the Gateway Tunnel under the Hudson River blame Trump, who they say has backed away from his predecessor’s promises of federal funding and put regulatory hurdles in the project’s way.

1. What would Gateway do?

Double rail capacity between Newark, New Jersey, and New York’s Penn Station -- the biggest bottleneck for train traffic on the East Coast -- by digging a new rail tunnel under the Hudson River and rebuilding the single existing tunnel. It would also replace a century-old swing-span bridge over the Hackensack River, the Portal Bridge, whose malfunctioning can strand tens of thousands of travelers. Gateway also would add new tracks and concourses at Penn Station, the nation’s busiest train depot.

2. Why is it seen as so urgent?

Time, salt and traffic. The existing North River tunnel opened in 1910. It is used by Amtrak for its Northeast Corridor service and by NJ Transit for its New York-bound service, and handles about 450 trains, or 200,000 passenger trips, a day. The 2.5-mile (4-kilometer) tunnel consists of two single-track tubes. During Hurricane Sandy in 2012, the tunnel was inundated with corrosive saltwater, bringing mass transit to a halt for days. The tunnel was restored to service, but corrosive substances from the saltwater remain in its concrete liner and bench walls, causing cracks and weakening the power system.

3. How long can the tunnel last?

No one knows. In 2014, Amtrak engineers gave it a life expectancy of about 20 years, but officials warn that it could become unusable far sooner than that. To rehabilitate it, planners would need to close each tube for about two years, one at a time. Relying on one tube to provide two-way service would mean reducing peak service by 75%. The governors of New York and New Jersey say the loss could be catastrophic not just to the local and regional economy but would have a national impact, given the tunnel’s potential to be a chokepoint in a rail network serving an area that produces 20% of the nation’s GDP.

4. What would fixing this take?

About seven years for construction of the new tunnel, once all approvals are in place. Once that’s in service, the two existing tunnels would be renovated in turn. The estimated cost for all that is $12.7 billion. Replacement of the Portal Bridge would cost about $1.6 billion.

5. What’s the holdup?

Transportation officials in Trump’s administration say the project is ineligible for federal funding because New York and New Jersey haven’t committed enough local money. They’ve put it near the bottom of the list of projects vying for federal mass-transit help. But a review of federal project ratings shows that similar funding issues haven’t been counted against transit projects elsewhere. The two states say they had a deal with former President Barack Obama’s administration to split the cost of the project. Trump officials say no such deal exists.

6. Why has this process taken so long?

Officials began planning a replacement program in 1995. The project, called Access to the Region’s Core, or ARC, had been allocated state and federal funding equal to its estimated cost of $8.7 billion and was given an estimated completion date of 2018. Then New Jersey Governor Chris Christie, a Republican who ran for president in 2016, canceled it in 2010, citing concerns about potential cost overruns and a design that ended blocks from Pennsylvania Station. Critics said he killed ARC to use state funds to fund road projects that would have otherwise required an increase in the gas tax. Amtrak, the national passenger railroad, proposed Gateway in 2011.

--With assistance from Elise Young, Henry Goldman and Mark Niquette.

To contact the reporter on this story: Stacie Sherman in Princeton at sbabula@bloomberg.net

To contact the editors responsible for this story: Flynn McRoberts at fmcroberts1@bloomberg.net, John O’Neil

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