On a 95-degree day this summer, New York City’s Third Avenue Bridge, which connects the Bronx and Manhattan, remained open for hours. As heat and flooding scorched the Midwest, a steel railroad bridge connecting Iowa to South Dakota collapsed under surging water. In Lewiston, Maine, a bridge was closed after the pavement buckled from the fluctuating temperatures.
A quarter of America’s bridges built before 1960 were already in need of repair. But now, extreme heat and increased flooding linked to climate change are accelerating the deterioration of the nation’s bridges, essentially causing them to age prematurely, engineers say.
The result is a silent but growing threat to the safe movement of people and goods across the country, and another example of how climate change is reshaping daily life in ways Americans are unaware of.
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“We have a bridge crisis that is particularly tied to extreme weather events,” said Paul Chinowsky, a professor of civil engineering at the University of Colorado Boulder who studies the effects of climate change on infrastructure. “These are not things that would happen under normal climate conditions. These are things we have never seen before at this rate.”
Bridges designed and built decades ago with materials that could not withstand sudden temperature changes now begin to swell and shrink rapidly, weakening them.
“It’s getting so hot that the pieces that hold the concrete and steel together, the bridges, can crumble like Tinkertoys,” Chinowsky said.
As temperatures hit their highest levels on record this year, much of the country’s infrastructure, from highways to runways, has been damaged, but bridges are particularly at risk.
“With bridges, you’re working with infrastructure that may have been planned, designed and built decades ago,” Transportation Secretary Pete Buttigieg said in an interview. “It’s one of the longest-lasting forms of infrastructure to update or replace. And yet we see these vulnerabilities all over the country.”
A study published in the journal PLOS ONE found that extreme temperatures from climate change could cause 1 in 4 of the steel bridges in the United States to collapse by 2050. By 2040, failures caused by extreme heat could require widespread bridge repairs and closures, the researchers found.
Another study found that exposure to extreme temperatures is causing pavement on American bridges to buckle. Meanwhile, heavy rainfall linked to climate change is increasing the phenomenon of “bridge erosion,” the erosion of soil sediment around bridge foundations that is a leading cause of bridge failure in the U.S., studies show.
The troubled bridges are starting to affect supply chains and the cost of goods. In 2022, a 30-foot section of Interstate 10 bridge on the California-Arizona border, along a major truck route from Phoenix to the Port of Los Angeles, was washed away during record rainfall. That flooding followed the collapse of another Interstate 10 bridge, the Tex Wash Bridge, in 2015, in what was then described as a once-in-1,000-year flood. Each closure adds an estimated $2.5 million a day to trucking costs because of delays and additional fuel, according to the American Transportation Research Institute. Engineers say such bridge closures are projected to increase significantly nationwide in the next decade.
“With a lot of these bridge closures, trucks are having to reroute a lot more than they normally would. That adds 15 to 100 miles per trip, whereas the cost of a truck trip is typically about $91 per hour,” says Dan Murray, senior vice president of the American Transportation Research Institute. “And it becomes very inflationary. We’re buying the same stuff, and the unexpected costs are being passed on to consumers.”
Bill Minor, a 50-year-old Walmart truck driver who delivers groceries, clothing and electronics from a terminal in Beaver Dam, Wisconsin, to nearby stores, said he crosses the Lake Butte des Morts Bridge in Oshkosh, Wisconsin, as many as a dozen times a day. When the bridge was closed for a day in June because of the heat, widening a joint on the approach to the bridge, Minor said the added detours and traffic caused him to make fewer deliveries and use more fuel.
“The bridge is on an interstate but the road is a rural road, so you’re going through small towns at 25 miles an hour,” he said.
The Biden administration has sought to address the issue. The 2021 bipartisan infrastructure bill earmarks $110 billion for repairing and building roads, bridges and other major transportation projects. The law includes a flagship program, PROTECT, that provides $7.3 billion, divided among states, to make facilities and highways more resilient to extreme weather. Another $1.4 billion is available in competitive grants.
In Vermont, where heavy rain and heat combined to damage about 100 bridges in the past two years, the state is rebuilding bridges higher and wider, with deeper foundations and sturdier materials, and the waterways beneath the bridges are being made deeper and wider to absorb more water.
But all of that takes money and time. It would cost Vermont 30% to 40% more to build a more flood-resistant bridge, said Jeremy Reed, chief engineer for the state transportation agency.
Scientists, engineers and government organizations are just beginning to develop standards for how to build climate-resilient bridges, said Jim Tymon, executive director of the American Association of State Highway and Transportation Officials. “We learn from the events that are thrown at us and try to change and build according to what climate change brings next, but it’s a moving target,” he said.
In 2018, Colorado became one of the first states to consider the effects of climate change when planning its roads and bridges. After a 2013 flood damaged nearly 500 miles of roads and 50 bridges in the state, requiring more than $700 million in emergency repairs, the state transportation commission required climate resilience in bridge and road construction.
The state asked Hussam Mahmoud, a civil engineer and professor at Colorado State University, to examine the increasing deterioration and stress at the joints of the state’s steel bridges. “What we saw was very drastic,” Mahmoud said.
For decades, bridge surfaces have been zippered together with clevis expansion joints embedded in the steel and pavement to accommodate the normal swelling and contraction that occurs with heat and cold.
But Mahmoud said the joints were swelling more and more frequently due to extreme temperature increases linked to climate change. The problem was made worse by overheated joints expanding tightly around road debris that had accumulated between them. “When that happens, the bridge can be permanently damaged,” he said. “The steel deforms and bends, the deck cracks and moisture seeps through, causing corrosion.”
Swollen joints cause other problems. Steel bridges are designed to bend slightly to accommodate heavy loads, but blocked joints keep the beams rigid and unable to spread the load from large trucks.
“This means that the beams on the bridge are carrying much more weight than they were designed for,” Mahmud said.
Age is often one of the best predictors of bridge fragility. Engineers typically prioritize bridges for repair and replacement once they pass the age of 50.
Mahmoud was surprised to find that the Colorado bridges in worst condition include an 18-year-old bridge over the Riverside Canal in Morgan County, a 29-year-old bridge on County Road 501 through Pueblo County and a 10-year-old bridge on County Road 17 over the Otero Canal in Otero County.
All of these bridges were deemed in “good” or “satisfactory” condition as a result of inspections conducted between 2020 and 2022, according to the Federal Highway Administration’s National Bridge Inventory.
Colorado transportation officials say they now factor in such studies when prioritizing which bridges to fix, but the state doesn’t have the funds for all those upgrades. Under the infrastructure law, the state gets $45 million a year in federal funds for bridge repairs and $98 million a year from the PROTECT program to make all of its infrastructure more climate-resilient by 2026.
State officials estimate Colorado probably needs more than five times that amount annually. “Realistically, we know that’s not going to happen,” said William Johnson, who leads climate resilience programs for the Colorado Department of Transportation. “We can’t change everything tomorrow to be more resilient, but we are factoring in climate change.”
Mahmoud expanded his research nationwide, using details from the National Bridge Inventory to model the impact of climate change on the girders, decks and beams of 80,000 steel bridges. He found that the bridges most at risk were in the Northern Rockies and Plains, the Upper Midwest, the Ohio Valley and the South. He also found that smaller bridges with smaller girders were more vulnerable to damage because they were built to carry lighter loads.
The bridges in Mahmoud’s database include 1,357 steel bridges in Oklahoma and 575 in North Dakota, including a 25-year-old bridge over the North Branch Goose River in Traill County, North Dakota, a 16-year-old bridge on a county highway through Grand Forks County, North Dakota, and an 11-year-old bridge on Route E0220 in Grant County, Oklahoma.
“These bridges in these states were designed to code,” Mahmoud said. But because of the unplanned damage caused by climate change, “we will see beams on these bridges buckle, concrete fall and bridges close.”
North Dakota state bridge engineer Jason Thorenson said he disagreed with Mahmoud’s reference to North Dakota bridges being at risk. He said the state receives about $45 million a year from the PROTECT program, “but I can’t say we’re using that money to address any climate change, because I can’t say we’re actually seeing it.”
Tim Gatz, deputy director of the Oklahoma Department of Transportation, said that in addition to cold, heat can also put a strain on roads and bridges. “We’ve had a lot of different weather conditions all the time,” he said. “Sometimes it’s extremely cold, sometimes it’s extremely hot.”
Royce Floyd, an engineering professor at the University of Oklahoma, said studies have shown that climate change is causing faster swings between extreme heat and cold. Floyd found that these seesaw temperatures can cause pavement to squeeze into an opening on either side, causing the road and steel to buckle or crack, or even cause steel beams to move out of alignment.
The same thing has happened to at least three major bridges in Oklahoma in recent years, he said. The bridges have since been repaired — without taking into account studies of current and future effects of climate change. But not making them more resilient means the buckling could return, Floyd said.
“If you don’t plan for climate change, you will face the same problems again,” he said.
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