President Biden on Monday announced that more than $4 billion in federal infrastructure money will help to replace the Baltimore and Potomac Tunnel, a crucial piece of the Northeast rail network that is a source of delays 150 years after it was built.

The Reconstruction-era tunnel — the oldest in the Northeast — is Amtrak’s biggest chokepoint between Washington and New Jersey. Trains crawl at 30 mph through its curves under West Baltimore, creating delays up and down the busy Northeast Corridor. When a new tunnel is complete, trains will reach speeds of 100 mph.

Biden visited to the decrepit structure Monday in the first of three stops this week to highlight projects that will benefit from the $1 trillion infrastructure law he signed in 2021. He pledged that the new federal aid will help to launch tunnel construction as early as this year.

“The structure is deteriorating. The roof is leaking. The floor is sinking. This is the United States of America, for God’s sake,” said Biden, recalling delays he encountered at the tunnel during decades of commutes between Delaware and the Capitol.

Biden’s visit marks a milestone in getting the project to construction and comes as the administration is beginning to distribute billions of federal dollars to upgrade aging infrastructure. Biden, who rode Amtrak for more than three decades while in Congress, has been a longtime supporter of investment in passenger rail while advocating for modernizing the Northeast Corridor.

The tunnel is a major bottleneck for Amtrak, Maryland commuter trains and freight rail traffic that moves between Baltimore’s Penn Station and points south, while a plan to replace it has been delayed for years, without viable funding. The infrastructure law provides $66 billion for rail, an unprecedented boost in federal aid for trains and a turnaround for a railroad that has struggled to draw financial support.

The White House said funding from the infrastructure law could contribute up to $4.7 billion of the Maryland project’s estimated $6 billion cost. It is also expected to create 20,000 construction jobs.

“For years, people talked about fixing this tunnel,” Biden said. “This is a 150-year-old tunnel — you wonder how in the hell it’s still standing. And with the bipartisan infrastructure plan, we are finally getting it done.”

Demolition, utility relocation and some track work will begin this year, officials said. In June 2021, Maryland and Amtrak announced a deal to move forward on a replacement plan within the decade.

Amtrak plans to build single-track twin tunnels that would arc about a half-mile north of the existing tunnel. The carrier has been working on the design and negotiating property acquisitions, while promising that the tunnel — to be named after Maryland native and abolitionist Frederick Douglass — will carry electric-powered trains to reduce environmental effects on nearby Baltimore neighborhoods.

Once completed, capacity in the Amtrak-owned tunnel would nearly triple while trains would pass through much more quickly. Officials estimate a new structure would mean average savings of seven hours of train delays on weekdays.

“It’s hard to overstate what a big deal this is for Maryland,” Sen. Chris Van Hollen (D-Md.) said in a statement. “Replacing this tunnel with the new Frederick Douglass Tunnel will not only improve rail service for travelers and commuters it will also drive more growth and opportunity to our state by slashing the travel time from D.C. to Baltimore to just 30 minutes and expanding business at the Port.”

Sen. Ben Cardin (D-Md.) praised the investment as trains passed by Monday afternoon. He said the project is critical to improving transportation for thousands of train users.

“The person who knows this best is Joe Biden because he’s been stuck by the delays in this tunnel many times as a passenger of Amtrak,” Cardin said. “This tunnel will provide the future that we need in a modern way to deal with passenger rail in our community.”

Although no specific funding allocations have been announced, the Department of Transportation late last year identified the Baltimore project among more than a dozen century-old bridges and tunnels in the Northeast set to receive $9 billion through a grant program — one of several funding sources.

The tunnel project already has received $44 million in federal funding for preliminary engineering and permitting, and Maryland has committed to contributing $450 million.

At Monday’s event, officials also announced multiple labor agreements they say will assure good jobs and lower the chances of labor disputes that could delay construction. Biden was joined by Transportation Secretary Pete Buttigieg, Amtrak leaders and Maryland Gov. Wes Moore (D).

On Tuesday, Biden will travel to New York to highlight investment in a Hudson River rail tunnel. Infrastructure money is expected to help fund a new tunnel and rehabilitate an existing tunnel that carries more than 400 trains daily between New Jersey and New York. The structure has been in use for more than 110 years and suffered saltwater damage in 2012 from Hurricane Sandy.

Biden and Vice President Harris will be in Philadelphia on Friday to promote clean water initiatives supported by the infrastructure law.

The Maryland and New York-area projects are at the top of Amtrak’s priority list and would reduce travel times between Washington and Boston, a corridor that is the spine of Amtrak’s operations.

Of the 15 century-old bridges and tunnels on a list of “major backlog” projects in the Northeast, the B&P Tunnel is by far the oldest. It opened in 1873, when Ulysses S. Grant was president, and is constructed out of brick and stone masonry. It was last rehabilitated in the 1980s, and according to federal documents, requires “continual repairs” to maintain.

A 2011 report found that “the physical condition” of the tunnel required that it be rebuilt or replaced within the next 10 to 20 years. The Federal Railroad Administration has declared the tunnel structurally deficient and unable to meet projected demands.

It has critical structural problems, including water issues and brick deterioration, according to a federal review of the project. Water-saturated soil beneath the tunnel is causing its floor slabs to sink, forcing Amtrak to make costly and repeated repairs. The tunnel also requires frequent inspections and maintenance to keep operations safe.

The 1.4-mile tunnel is a crucial piece of the network connecting Washington to Boston, moving more than 259 million passengers each year. Because there are no alternative tracks for passenger trains, officials said a tunnel outage would be catastrophic for train travel in the corridor. Passengers moving through it encounter chronic delays: More than 10 percent of weekday trains are behind schedule and delays occur on 99 percent of weekdays, according to the White House.

Officials estimate a new tunnel would reduce travel times on trains between D.C. and Baltimore to 30 minutes, down from about 40 minutes today. Biden said that could induce more people to take trains instead of driving, a move that also would bring environmental benefits.

“This is just the beginning of having a 21st century rail system that is so overdue in this country,” he said.