Around 175 million tons of freight travels on the Mississippi River each year, and from the river’s headwaters to southern Illinois, a series of locks and dams guide barges through the journey.

Traffic is only increasing, but the locks and dams have aged far past their life expectancy. Even functioning properly, they slow barges down, and shippers and commodity groups fear a worse infrastructure breakdown is on the horizon.

“Is it a matter of if you have a failure … or when you have a failure?” said Mike Steenhoek, executive director of the Soy Transportation Coalition.

Steenhoek likened the system to a fire hydrant hooked up to a garden hose. Since the locks and dams were built almost a century ago, farmers are producing significantly more corn and soybeans for export.

Those commodities are loaded up on barges and pushed by towboats, which must enter each lock as they make their way along the river. The locks allow the boats to gradually adjust to changing river levels. Most towboats can push 15 barges at a time on the river. But when those barges reach a 600-foot long lock, they don’t fit. Instead, they have to be split up, which takes more than twice as long.

Those delays keep growing. A 2019 Agribusiness Consulting report found that in 2017, more than half of boats and barges on the river were delayed at locks and dams, up from about one in five in 2000. Delay time increased from 90 minutes to about 122 minutes, some of the longest delays in the country.

Steenhoek said farmers ultimately foot the bill. If shipping companies face slowdowns on the river that cost them more in fuel, they’ll lower the price they’re willing to pay farmers for the product.

Almost everyone involved can agree that something needs to be done about the locks and dams, which have an estimated billion-dollar backlog of maintenance costs.

Yet with so many varied interests, the question of who should pay – and what exactly to pay for – isn’t as easy to answer.

“We’re doing repairs … to keep it operational,” said Kristin Moe, navigation business line manager for the U.S. Army Corps of Engineers’ St. Paul District. “But at some point, we’re going to need some major rehabilitation of these structures.”

Locks and dams far past expected lifespan

As the Midwest’s agricultural and manufacturing economies developed in the 20th century, it became increasingly hard to move goods on the upper river, which at times was so shallow that people could walk across it. As early as the 1830s, there was interest in controlling the river’s whims to give commercial traffic easier passage.

In 1930, Congress approved a project that would ultimately create the current system of 29 locks and dams that stretches from Minneapolis to Granite City, Illinois. The upper river is divided into sections called pools, where a fixed amount of river is held back by a dam. The Army Corps controls how much water is in a pool at a given time, which must be at least nine feet deep to allow barges to move through.

Between the headwaters in northern Minnesota and Granite City, the river falls about 420 feet in elevation. Each lock acts like an elevator, bringing boats up or down to the water level of the next pool.

The lower river does not have locks and dams. As major rivers like the Missouri and the Ohio join up with the Mississippi, the channel becomes deep and wide enough to naturally accommodate shipping.

At the time that the locks and dams were constructed – mostly between 1930 and 1940 – engineers estimated their lifespan to be about 50 years. Today, they’re pushing 100 years old.

If the upper Mississippi River had to shut down for one season because of lock and dam failures, the amount of agricultural goods displaced would equal between 367,000 and 489,000 loads by truck, according to a 2018 study from the University of Wisconsin-Madison. Turning to other modes like trucks and rail could be costly.

And as the infrastructure ages, there’s also another piece of uncertainty to contend with: the changing climate, which brings with it more weather extremes. Last fall, intense drought halted barge traffic on the lower Mississippi River, and this spring, widespread flooding on the upper river did the same thing.

“Having this pendulum swing … it’s very jarring to anyone who uses the system,” Steenhoek said.

Those changes make it even more important to do preventative maintenance of the locks and dams, he said.

Groups disagree on what projects to fund

Taxpayers have been funding inland waterway navigation for nearly two centuries, but Congress established the Inland Waterways Trust Fund in 1978, which required the private shipping industry to pitch in.

Today, the trust fund’s coffers are filled by a 29-cent per gallon diesel tax on commercial operators that use the Mississippi River and other inland waterways. New construction is paid for through a public-private partnership: the private dollars in the fund, which cover 35%, and federal dollars, which contribute 65%.

But once the projects are completed, it’s taxpayers who pick up the tab for maintenance and repairs through federal funds. Thus the debate becomes not only who pays, but what projects should be paid for.

“We don’t need new waterways infrastructure,” said Olivia Dorothy of American Rivers. “We don’t need new dams. We don’t need new locks. We don’t need new stuff. We need to maintain the stuff that we have.”

American Rivers has long advocated for private industry to pay for maintenance, given that it’s directly benefiting.

The Inland Waterways Trust Fund is the most successful effort in Dorothy’s eyes, but it doesn’t require the industry to pay for maintenance, which is the biggest expense. That includes a long list of backlogged projects, like repairing concrete walls and replacing gates. American Rivers argues that the companies using the waterway the most should pay the most to maintain it, similar to the highway funding model, which leverages fuel taxes, vehicle registration fees and other fees.

Those who represent shippers – like the Waterways Council, a public policy group that advocates for an efficient inland waterways system – disagree. Deb Calhoun, the group’s senior vice president, said the system should be modernized so that every lock has a 1,200-foot chamber, which would allow today’s larger tows to move up and downriver faster.

Federal infrastructure law funding will pay for at least one of those larger chambers, at Lock 25 in Winfield, Missouri. It’s the first lock chamber project to be funded from an Army Corps effort to address navigation concerns along with environmental ones.

Because the amount of goods traveling on the river is expected to increase, money shouldn’t be spent on rehabbing existing structures, but instead on building new ones, Calhoun said.

The Waterways Council is opposed to additional toll or lockage fees for shippers that use the river. Calhoun said it’s not just shippers who benefit from an efficient river.

“The Mississippi River is a natural gift to the U.S., and it has beneficiaries like recreational boating and fishing, waterfront property development, and water for manufacturing processes,” she said. “None of those beneficiaries pay for the dedicated fuel tax.”

Proposed funding model would have shippers pay up front

Amid disagreements over funding, one proposal by an Iowa State University professor puts a spin on the public-private partnership model, asking shippers to foot some of the bill up front for lock and dam repairs in return for easier passage on the river.

Yoshinori Suzuki, the school’s Land O’Lakes Endowed Professor of supply chain management, argues that the up-front payment would skirt the prohibition of river tolls in a study published in January in Transportation Journal.

Suzuki ran simulations of upper Mississippi River traffic flows through a mathematical model to figure out how much shippers would have to pay to get the highest return on their investment. If they covered between 60 and 80% of the cost, he found, they could maximize their investment and be paid back in eight years or less.

Suzuki said his model is already of interest to shippers. The study was paid for by Iowa State’s Supply Chain Forum, which includes corporate partners like Land O’Lakes, Cargill and Kent Corporation. Suzuki said companies are “deeply concerned” with the aging system, and that they were interested in the idea even before he presented the results.

“Most, if not all, are very willing to provide funding to this kind of project as long as the investment comes back in positive return,” he said.

Land O’Lakes and Kent Corporation did not respond to a request for comment about the study findings. A spokesperson for Cargill said the company had not yet been presented with the research.

Suzuki acknowledged that there’s a lot left to figure out before his proposal could be put into action, like who would ultimately approve such a funding model and which entity would be in charge of spending the money.

The model also relies on all shippers who use the river pitching in, which could take significant convincing. Calhoun, with the Waterways Council, said she felt doubtful it would come to pass.

Moe said the Corps is open to partnerships that could help them explore more innovative ways to fund repairs, including a public-private one.

And in the meantime, they’ll keep chipping away.

“It’s just a matter of, can the funds keep up with this growing maintenance backlog?” she said. “This aging infrastructure is getting older every day.”

This story is a product of the Mississippi River Basin Ag & Water Desk, an editorially independent reporting network based at the University of Missouri School of Journalism in partnership with Report For America and the Society of Environmental Journalists, funded by the Walton Family Foundation.