The U.S. is home to some truly ambitious infrastructure megaprojects, defined by the Department of Labor as projects that are "valued at $35 million or more in funding, some part of which must be federal funding, and are expected to last for at least one year."

Here are five of the biggest and most expensive projects on the horizon.

Project Apex

The billion dollar Project Apex – Integrated Sustainable Battery Active Material and Precursor Production Plant in Kentucky is slated to establish the industrial scale production of materials to equip up to 250,000 electric vehicles per year. When the project is fully realized, this number is expected to surge to 750,000.

According to the Department of Energy, the plant will focus on manufacturing sustainable, low-cost precursor cathode materials by integrating the separation of critical cathode materials from spent lithium-ion batteries with the production of both precursor cathode materials and metal salts to support domestic production of cathode active materials.

The project, based in Hopkinsville, is currently scheduled for completion in 2025.

Midwest, Appalachia, California and Texas hydrogen hub projects

Plans for hydrogen production construction projects spanning the US are currently in the works, with plants earmarked for the Midwest, Appalachia, Texas and California some time in the future.

All-in-all, the array of new hubs will cost somewhere in the ballpark of $4.5 billion. The Appalachian hub will receive a federal cost share up to $925 million, the Midwest hub up to $1 billion, and the Texas and California hubs $1.2 billion, Construction Briefing reported.

These projects are still in the preliminary phases. As of yet, there are no set construction dates.

Brightline West High-Speed Intercity Passenger Rail System

The Brightline West High-Speed Intercity Passenger Rail System, which just recently started construction is aimed at connecting Las Vegas, Nevada, to Southern California through a 218-mile route.

The rail line is expected to significantly cut travel times compared to driving, offering speeds up to 200 miles per hour and covering the distance in approximately two hours.

The project's total investment is estimated at $12 billion. It is slated for major construction to begin in 2024 with an anticipated completion date around 2028, aligning its opening with the Los Angeles Olympics.

Brightline, known for operating the high-speed rail in Florida, leads the project, which is funded through a mix of federal grants and private investments.

Hudson Tunnel Project

The Hudson Tunnel Project is slated to cost more than $16 billion and has already received $12 billion in federal funding.

The project is aimed at enhancing rail connectivity between New Jersey and New York by constructing a new two-track rail tunnel under the Hudson River and rehabilitating the existing 113-year-old North River Tunnel, which was severely damaged during Superstorm Sandy in 2012.

A spokesperson for the Gateway Development Commission told Newsweek that, "Daily commuters currently rely on an antiquated, damaged 'one-track-in, one-track-out' tunnel that is not equipped to serve our modern economy – especially not for a region that contributes to 20% of the national GDP."

The new tunnel will ensure that there is redundant capacity, allowing for one tunnel to be taken out of service for maintenance without significantly disrupting the daily transit of hundreds of thousands of commuters and travelers along the Northeast Corridor, which is one of the busiest rail corridors in the U.S.

Construction of the new tunnel is anticipated to begin in earnest in 2024, with major construction efforts expected to ramp up following the completion of preliminary work and securing final funding agreements. The projected completion and opening of the new tunnel are set for 2035.

"The Hudson Tunnel Project is a generational investment that is expected to create 95,000 new jobs and generate nearly $20 billion in economic activity over its construction period," the spokesperson said.

California High-Speed Rail

The California High-Speed Rail project seeks to connect major cities across the state with a high-speed train system. It is currently projected to cost $135 billion.

The rail system could connect cities like San Francisco and Los Angeles with trains traveling up to 220 mph, making the journey between these two cities in under three hours. The first stretch of the project aims for completion by 2030.

The first segment of the rail system alone is set to span 171 miles of the Central Valley region (Merced to Bakersfield), with further additions later down the line.

However, it seems that the bigger they are, the harder they fall, and the ambitious rail system's construction has been marred by setbacks since its 2008 inception.

Initially, the project was challenged by underestimations of the cost and complexity involved. Over time, the budget ballooned from early estimates, leading to fiscal concerns and political debates about the project's viability. Funding issues have been a persistent problem, with the project not always securing the necessary financial support to proceed as planned.