President Joe Biden signed the infrastructure bill into law in November 2021. However, with inflation at a 40-year high, billions of dollars have already been lost from the $1.2 trillion earmarked for upgrading America's roads, sewers, airports, bridges and dams. States are having to delay or cancel projects they had planned to build. Thankfully, a number of ambitious megaprojects are already under construction. From high-speed rail in California to America's first nuclear power plant in more than 30 years, read on to discover some of the biggest projects currently under construction in the US – and when we might expect them to finish. 

Chicago’s ambitious Tunnel and Reservoir Plan (TARP) isn't just one of the biggest megaprojects in America – it's also one of the largest in the world.

The huge civil engineering project centers on a system of deep, large-diameter tunnels and vast reservoirs, designed to reduce flooding and clean up the local waterways. TARP collects and stores combined stormwater and sewage that would otherwise overflow from sewers into waterways when it rains. This water is then pumped from TARP to plants, where it is cleaned and released.

The project was first commissioned back in the 1970s with completion expected in the 1980s. However, construction of the sewer system is still ongoing and the completion date has now been delayed to 2029, meaning the project will have taken well over 50 years to finish.

Chicago planned four systems totaling 109 miles of drainage tunnels – all measuring in at 8ft to 33ft in diameter and 150ft to 300ft underground – with the project to be built in two phases.

The Phase I tunnel systems went into service as portions were completed; work started in 1975 and was completed by 2006. Phase II, which should be finished within the next seven years, is focused on building three huge reservoirs for flood control, and will bring the total TARP storage volume to 17.5 billion gallons.

Chicago has already seen dramatic improvements in its water quality. Game fish have returned, and this has led to the opening of marinas and riverside restaurants. In fact, river recreation and tourism are booming, as are waterfront real estate prices.

TARP has won numerous awards for its engineering, including the American Society of Civil Engineers' Most Outstanding Civil Engineering Project. It has also won acclaim for its environmental impact.

To cite an exact cost for the megaproject is difficult due to the sheer length and scale of the work. However, hundreds of millions of dollars have apparently already been saved by reducing flooding in the city thanks to TARP.

Back in 2008, California's voters approved a $9.95 billion plan to start building a high-speed rail network across the state.

The fully-extended system would comprise 800 miles linking Sacramento and San Diego, and the 500-mile connection between San Francisco and Los Angeles is expected to have a journey time of just under three hours. This ambitious project was initially estimated to cost around $40 billion in total, but it has been plagued with difficulties...

Due to a series of protests and lawsuits, the construction of the first 119-mile Central Valley section, between Merced and Bakersfield, didn’t start until 2015 – almost three years behind schedule. And as the timeline of the megaproject has increased, so too has its budget.

This initial section is considered the backbone of the entire system. Even though portions of the line have been under construction over the last seven years, the final track alignment is still unconfirmed. The rail agency now predicts the Central Valley section alone could cost $23 billion and won't open before 2029. 

On top of those delays, the project lost time and money from the impacts of the COVID-19 pandemic and budget cuts brought in by the Trump administration. Though progress is being made in other ways on the 171 miles that are currently under development and construction in the Central Valley. The rail agency recently announced it completed three high-speed rail grade separations. 

However, high speed rail travel between San Francisco and Los Angeles and Anaheim is now expected by 2033, and the price tag is predicted to reach as much as $113 billion.

The Vogtle Electric Generating Plant, otherwise known as Plant Vogtle, is a nuclear power plant in Waynesboro, Georgia.

Units 1 and 2, which consist of a pressurized water reactor, steam turbine and electric generator, were both completed back in the late 1980s.

Collectively, the pair of units can generate 2,430 megawatts of electricity and cost an astonishing $8.87 billion to build. That's the equivalent of around $23 billion in 2022. 

And the total cost of the plant is rocketing again, as Units 3 and 4 are currently still under construction. These two new units are the first nuclear power plants to be built in the US in three decades and initially carried a price tag of $14 billion.

The planning application process took three years, with building work finally beginning in 2009. According to the initial schedule, Unit 3 would be operational by 2016, followed by Unit 4 in 2017. But that hasn't been the case... 

Japan's 2011 Fukushima disaster caused construction to falter due to safety concerns and lawsuits from anti-nuclear campaigners. Although the legal action was thrown out, it wasn't the end of Plant Vogtle's problems.

American nuclear power company Westinghouse, which was responsible for designing, engineering and managing the megaproject, went bankrupt in 2017, and construction was taken over by Southern Nuclear. Further delays followed and the cost of the new units has ballooned to $30 billion – more than double its original budget. 

However, there is good news. Construction is complete on Unit 3 and in October 2022 the federal government approved loading the radioactive fuel rods needed to generate power. Unit 3 is expected to finally enter service in early 2023, with Unit 4 following later in the year.

Voted through in November 2020, Project Connect is an ambitious plan to expand the transport links in Austin, Texas.

The original proposal suggested it would cost around $10 billion but due to concerns stemming from the COVID-19 pandemic, the project was scaled back and will now cost around $7.1 billion. This budget includes the construction of two light rail lines, a commuter rail line and a rapid bus line, as well as improvements to existing infrastructure. 

A major component for the Project Connect program is a transit tunnel through downtown Austin for the two proposed light rail lines, along with subsurface stations. Building infrastructure underground has proven to make megaprojects even more likely to run over budget, and Austin is no exception. Initially estimated at $2 billion, the tunnel costs have already doubled to $4.1 billion over the last two years due to inflation and design changes.

While Austin broke ground in February 2022 on its MetroRapid Pleasant Valley bus route, much of the Project Connect program is still in the design phase.

And while it hasn't faced the logistical nightmares and lawsuits as seen on other projects on this list, the overall delivery timeframe is still unclear, except that the new light rail lines are not expected to open before 2030. Meanwhile inflation is already creating record-breaking cost increases for the construction industry, and Project Connect is not immune. The estimated price is now up to $11 billion, which is more than what was budgeted before the pandemic-related cuts.

Schedule delays have plagued New York’s first major commuter rail expansion project in 100 years.

The East Side Access (ESA) program aims to tackle severe overcrowding at Penn Station by providing new commuter rail service from Long Island and Queens to Grand Central Terminal (GCT) in Midtown Manhattan.

This mammoth megaproject includes a new eight-track terminal and concourse below GCT, 13 miles of tunneling, 40 miles of new track, a new storage yard for 300 trains and new bridges at a major junction, among a lot of other construction work. 

Undertaking construction work in the country's biggest and busiest city is never going to be easy. However, one of the largest hurdles for the ESA seems to be delays and price increases. Dating back to the 1950s, a lack of funds had left the project stalled for decades. In the 1990s a New York governor proposed reviving the project, expecting a $4.3 billion price tag with construction completed in 2009.

Lining up funding and permits, among other challenges, meant the MTA's Construction & Development Company didn't break ground on the megaproject until 2006. 

As construction continued on the various ESA projects over the last 15 years, the program's final cost steadily grew. By 2012 it had doubled to $8 billion. Now it's expected to come in around $11.1 billion. And the end is in sight. All of the major engineering work for infrastructure, like the tunnels and underground station caverns, is completed. The project says it is aiming to be open by December 2022, however, it has been revealed a safety feature won't be installed in time. Without this, the federal government can't sign off the completed project, possibly delaying the opening to March 2023. The MTA successfully arranged a last minute exemption, which allows service to start, but the part must be installed by February. No specific date has been announced for the grand opening.

The Los Angeles region is rapidly expanding its subway and light rail services. The city's Purple Line Extension alone will add seven new stations and 9 miles of tunnels to connect downtown LA and the westside, including Beverly Hills, under Wilshire Boulevard. This project is being built in three sections, with the final construction work completed by 2027 in anticipation of the city hosting the 2028 Olympics.

Price estimates are set at $9.5 billion for the total extension.

Two of the project's phases include constructing tunnels below the ritzy Beverly Hills neighborhood, home of glamorous shopping mecca Rodeo Drive. Residents have been opposed to the megaproject, bringing various lawsuits and even staging walkouts with students from the local high school in protest of the subway line extension. The school district has spent as much as $15 million trying to block or alter the route of the subway. Despite this opposition, the megaproject has attempted to keep its tunnel boring machines moving...

Although not so successfully. While construction in the heart of Beverly Hills did break ground in 2019 for phase 2 and the final section in 2021, the phase one opening has been delayed by one year due to problems with ground conditions along the route. The machines excavating the 22ft-diameter tunnels had to pass through sand, tar and methane gas pockets near the La Brea Tar Pits.

More recently, work came to a complete halt in October 2022 when the county transport agency flagged up safety issues, including worker injuries and workplace hazards. The contractor has been cleared to restart construction as of November 18, roughly a month later.  

Many more miles of similar diameter tunnels are being built deep underground in Indianapolis. Instead of carrying subway passengers, these will transport polluted wastewater so it doesn't flow into local rivers before it can be treated, especially during storms. The $2 billion project is called DigIndy and includes 28 miles of 18ft-diameter tunnels, along with other sewer infrastructure like deep shafts (pictured), around 250ft below ground. 

The project has been ongoing over the last two decades as the city attempts to meet strict quotas on wastewater overflows that it negotiated with the Environmental Protection Agency (EPA) back in 2006. These agreed-upon DigIndy projects must be completed by December 2025. And the hefty $2 billion price tag has meant higher water rates for the city's residents. With four of the six tunnels that make up the system currently online, this megaproject is actually on schedule and budget.

However, as the city nears the completion date, it's realized the multi-billion-dollar DigIndy tunnels may not be sufficient. With the system being designed more than 20 years ago its size and capacity are based on rainfall amounts from the 1990s. The Indianapolis region has since seen its average rainfall increase in that time, which means it may not be able to eliminate as many wastewater overflows into local rivers as it had hoped. This potential pollution not only runs afoul of the EPA agreements, but also sends harmful pollution into local waterways, preventing residents from enjoying water sports and other recreational activities. 

San Francisco International Airport is spending $2.4 billion to renovate one of its terminals, now called Harvey Milk Terminal 1 in honor of the gay rights activist and former elected official. The project includes demolishing parts of the existing terminal, installing new foundations and building the two-story structure that houses 25 new gates, a ticketing lobby and space for restaurants and shops, among other features. The construction work is phased with the first section opening in 2019 and the final work expected to finish in 2024. 

The original terminal dates back to the 1960s and had been struggling to keep up with the airport's growing passenger numbers. While it had been expanded numerous times in attempts to keep pace with air traffic, some areas also required seismic upgrades and there is limited land for the airport to expand.

Another significant component of the renovation project was to "revolutionize" the airport experience by creating spacious waiting areas filled with natural light and sourcing sustainable materials. The new terminal has a museum area, chaise lounge seating and space for yoga. Facilities that have already opened have scooped up credentials like LEED v4 Platinum Certification, the first in the world for an airport terminal.

With the pandemic slowing down construction the final phase is running about one year late. However, reduced flight demand over the last two years has meant airport revenue has plummeted, creating budget shortfalls. While this won't have an impact on the Harvey Milk Terminal 1 project, officials pulled the plug on a similar, glitzy $1 billion renovation for the airport’s Terminal 3. These works had been planned for a June 2020 groundbreaking, and after several delays, the airport announced in 2021 the upgrades have been put on hold indefinitely due to lack of funds.

From smart cities to transport overhauls, discover the world's most expensive megaprojects.