Autumn means rush hour on the Mississippi River, and this year looks to be even more frantic than most.

For barge shippers still reeling from one of the most difficult seasons in memory, and with a record corn and soybean harvest underway, one of the state's most important transportation links is being strained to its breaking point at a critical time of the year.

Some of the effects are being seen in supplies of cement and road salt, key commodities shipped upriver. Heading downriver, to which 60 to 70 percent of U.S. grain exports are shipped, silt has put a crimp on shipping capacity from Minnesota river ports.

While this year has presented a series of short-term problems, those who work on the river and know its economic importance to the state say it has put sharper focus on both the fragility of that transportation system and the urgency of updating its Depression-era infrastructure.

At least two Minnesota Department of Transportation road projects, on Hwy. 65 near Fridley and on Interstate 94 near Monticello, were disrupted by a lack of cement (to make concrete) when barge traffic was halted on the river. The problem also has affected local street projects and private contractors trying to get work done before winter.

"It's across the state, it's across North Dakota and Wisconsin — it's really an Upper Midwest issue," said Fred Corrigan, executive director of the Aggregate and Ready Mix Association of Minnesota.

Cement contractors are scrambling for supplies amid a perfect storm of problems at cement plants and a lack of transportation alternatives. Besides cement, contractors also need fly ash, a cement ingredient that mostly comes by rail from North Dakota, where oil industry transport has taken precedence. Trucks are limited by a driver shortage and weight limits that Corrigan's group would like eased.

Meanwhile, low salt supplies — and higher prices — are being blamed on high demand not keeping pace with production. Barges are the chief means of getting salt to Minnesota from plants in the South, and the shipping season typically stops by the end of November. Using other transportation modes would only add to the costs.

"We're very fortunate to have the river," Corrigan said. "It has the capacity, it's cheap — it's a great system."

A fragile system

Just how valuable — and vulnerable — that system is was made clear last summer when barge traffic was shut down for nearly three weeks starting in late July.

The closure followed a brutal winter that had navigation starting at its latest date since 1970 (excluding the flood year of 2001). Then came relentless rain and floods that swept along underwater mountains of silt that settled near the river towns of Wabasha and Winona. The U.S. Army Corps of Engineers estimates it cleared more than 290,000 cubic yards of dredged material, enough to fill a line of 10-cubic-yard dump trucks from Minneapolis to La Crosse, Wis.

Shippers on the Upper Mississippi not only lost that valuable time, but shoals clogging the shipping channel remain a problem, said Lee Nelson, president of Upper River Services in St. Paul, which moves barges between river terminals.

The Corps has been unable to widen the channel at a bend just upriver from Hastings, forcing shippers to shorten their loads from 15 to 12 barges. "This one spot right here is costing us 20 percent of our capacity," Nelson said, pointing to a river map.

Between the lost time and shorter loads, shippers have been pushing to counter those losses, said Richard Calhoun, marine and terminal division president for Cargill, the Wayzata-based agribusiness giant that operates a fleet of more than 1,200 barges on the river.

But while Nelson and Calhoun are used to dealing with the challenges each shipping season presents, both are deeply concerned about the long-term problems of the river's mostly outmoded infrastructure — and the devastating economic consequences of a prolonged river traffic closure.

"Most of the locks and dams, they came out of the 1930s," Calhoun said. "They were built for an economic life of approximately 50 years."

There are 21 locks on the Upper Mississippi River. If just one were to fail, Calhoun said, it would shut down the river for months. And those locks have two key disadvantages: They're only 600 feet long, forcing towboats to break up loads and go through half at a time; and they only have one chamber, meaning no backup if one breaks down.

If river traffic were to shut down, Calhoun said, Cargill would still find the means to transport grain to Southern ports. But the alternatives would be costly and the economic effects would be far-reaching, not just for shippers.

Finding solutions

Nelson and Calhoun are among those who are clamoring for improvements to the river infrastructure, and are willing to help pay to change the current fix-it-as-it-fails strategy.

Shippers pay a 20-cent-per-gallon tax to help pay for improvements, but funding has fallen far short of needs. In the Corps of Engineers St. Paul District alone, there is a backlog of $241.3 million in needed maintenance projects.

A bill co-sponsored by Sen. Amy Klobuchar, D-Minn., would increase that tax by 3 to 6 cents. A $12.3 billion water resources bill passed last spring that included the Red River Valley diversion project and the closing of the Upper St. Anthony Falls was a key first step, Klobuchar said, but also left most projects unfunded.

With about $7 billion in Minnesota farm exports annually, a market that could grow with the expansion of the Panama Canal, ensuring the Upper Mississippi stays open is critical, she said.

"It's not every day you have a group of people saying they want an increase in their fees," Klobuchar said of the river shippers. "They're saying, 'Yes, it gives us a higher fee, but it gives us the money we need for these upgrades.' "