DUBUQUE, Iowa — Persistent ice in the Mississippi River is delaying traffic along the waterway by about a month, say barge operators waiting for word on its opening.

Some operators like to begin sending their barges up and down the river in early March. But the bitter cold this winter and frigid start to the spring has changed the schedule. The Mississippi still has ice in a stretch of river that extends from Minneapolis to Clinton in eastern Iowa, according to the National Weather Service. The depth of the ice varies from 5 to 10 inches.

The National Grain and Feed Association gives official word on the opening of the river. Spokeswoman Heather McElrath said that declaration could come as early as April 1.

Commodity management company Gavilon, which operates barges, typically begins sending its barges of grain and fertilizer in early March.

The long winter could have a major impact on the year’s business.

“Any time you take a full 30 days out of the business structure, it is going to have an impact,” said Delbert Uhlik, the company’s Dubuque general manager. “Instead of a nine-month season, now you are talking about eight months.”

Rick Calhoun, president of the barge division for agriculture company Cargill, called the late thaw a “manageable delay.”

Operators like Gavilon have also utilized others forms of transportation in the meantime.

“We have been able to ship some grains on rail to limit our exposure, but it is nowhere near what the river system provides,” Uhlik said.

Officials for Lock and Dam No. 12, in Bellevue, Iowa, opened for business on Monday. They say they’re waiting for the first commercial shipping boats. Crews have worked for several weeks to break up river ice built around the lock gates.

“We’re ready for them, but we don’t know when the first one will get here,” said work leader John Williams.