The operators of a grain processing plant in southeast Iowa have agreed to pay a $4.1 million civil penalty for polluting the Mississippi River over more than a decade.

U.S. Environmental Protection Agency spokesperson Ben Washburn says the Iowa D.N.R. found Roquette America of Keokuk violated its National Pollutant Discharge Elimination System (NPDES) permit over 1,100 times and on at least 30 occasions, illegally discharged via storm drains.

“These discharges resulted in more than 250,000 gallons of untreated, industrial waste being discharged into the Mississippi River and Soap Creek,” Washburn said. The EPA accused Roquette of failing to construct additional containment structures for wastewater surges, or routing spills to the wastewater treatment plant.

Instead, Roquette allowed the industrial waste to be discharged directly into the Mississippi River and Soap Creek. “There are pretty serious violations and some pretty significant discharges,” Washburn said. “The discharges resulted in the Mississippi River color being changed from the clear blue to red in one place and a golden color in another.”

In addition to the civil penalty, Roquette must make $17 million in improvements to its facility. “They’ll be purchasing third-party monitoring, installing additional equipment and making various changes at their plant in Keokuk to prevent these kind of discharges from happening in the future,” Washburn said.

The Iowa D.N.R. issued three Administrative Orders and eight Notices of Violation to Roquette since 2000, but Washburn said Roquette continued to illegally discharge untreated industrial waste in the Mississippi River.