It's been years in the making: fully funding a second rail tunnel under the Hudson River.

Officials celebrated the last piece of $16 billion in funding for the Gateway Tunnel Project Monday, signing the nearly $7 billion full funding grant agreement with the U.S. Department of Transportation and securing the $4 billion in loans for the local match.

"The light at the end of the Gateway Tunnel is signed, sealed and delivered," Sen. Chuck Schumer said at a press conference.

In total, the project secured $12 billion in federal grants, the largest for a single transit project ever. But the impact will be much larger, with 95,000 union jobs needed to complete the project.

"Twenty billion dollars of economic impact. What does that look like? Oh, our local businesses are so excited, about families having more money in their pockets when times are tough, that they're going to spend on entertainment and restaurants and their kids' education," New York Gov. Kathy Hochul said at the press conference.

The second tunnel will eventually increase capacity and create a redundancy to prevent the nightmare so many commuters have recently experienced at Penn Station. Equipment failures near or in the current 114-year-old tunnel have brought train traffic to a halt.

"This is a game-changer," New Jersey Gov. Phil Murphy said. "The mom and dad who want to get home and have dinner with their kids, or help them out on their math homework. I think we need to think of this not just in the wow, big-number reality, what it will do for this region for both of our great states, but also the lives that will be transformed."

But that transformation can't come soon enough for the 200,000 people who travel between Newark and New York City each day.

While construction is already underway, it will be 10 years before the tunnel opens, and even then, the first tunnel will have to be closed to repair damage from Superstorm Sandy.