Iowa City resolves high levels of zinc after EPA violation

Iowa City water had high levels of zinc according to the Iowa Department of Natural Resources and violation of EPA guidelines. In response, daily zinc levels were lowered to stick within EPA guidelines.

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Ayrton Breckenridge

Water rushes out of the Coralville dam on Tuesday, Oct. 26, 2021.

Emily Delgado, News Reporter


In a response to the Environmental Protection Agency’s finding of violations in Iowa City’s water, the city has reduced the daily zinc intake to comply with federal guidelines.

High levels of zinc were found in water at the City’s South Wastewater plant in September.

Tim Wilkey, Wastewater Division superintendent, wrote in an email to The Daily Iowan that five years ago, the zinc levels that were allowed were 91.88 pounds per day. They have since been reduced to 44.1 pounds a day in response to the EPA’s letter. 

Zinc is an essential element in water, he wrote, but high levels are toxic.

“We found that we were having zinc issues and were reporting these to the [Iowa Department of Natural Resources] resulting in the Notice of Violation,” Wilkey said. “With the assistance of the EPA, we found the problem and were able to take corrective action with the source and come back in compliance.”

On Oct. 7, the City Manager’s Office released an Iowa City City Council memo regarding the letter of non-compliance sent by the EPA to the Iowa City Public Works Department. 

The memo stated the Iowa City Wastewater Division was going to send out a written certification to the EPA at the end of October, but they haven’t yet, Iowa City Public Works Director Ron Knoche said.

“We lowered our overall zinc limit that we had on the plant site and so with that and with understanding what the issue was, we were then able to work with our industry partners to get a better understanding of what the issues were and to determine what the appropriate loading limit was,” Knoche said. 

The cause of these violations was a mistake in calculations in how much the plant could take, not a treatment process issue, he added.

“It did not have an impact on the health of the community members,” Knoche said. 

The Department of Public Works’ solution was to work with industry partners to make sure they understand the limits they have when they are unloading industry discharges in Iowa City water.

“The numbers that we have for our effluent that goes to the Iowa River is based on the calculations that the Iowa DNR has for the amount of loading works they believe the river can receive from our plant,” Knoche said. 

Zinc enters bodies of water in three ways: anything that is discharged by residents and human discharge, as well as industrial discharge. In this case, the reason why high levels of zinc were found in the water was because of industrial discharge, Wilkey wrote. 

Since working with the EPA and industry partners, the Department of Public Works has not come across any overly high levels of zinc, Knoche said. 

“The Iowa City Wastewater Division has addressed the compliance issues as stated in the inspection report and will operate the treatment plant to meet the requirements of our NPDES operation permit,” Knoche wrote in the memo to the city council. 

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