Hills

On Friday, March 6, the Hills Community Center hosted a meeting on tile runoff monitoring led by Dr. David Cwiertny, a professor at the University of Iowa.

Cwiertny has studied agricultural tile drainage for several years and moved to Iowa from California in 2011. 

His research includes monitoring tile runoff in counties such as Muscatine, Scott, Washington and Cedar, which were discussed during the presentation.

During the meeting, Cwiertny used a projector to display data collected from several monitoring locations and explained how tile drainage systems move water and nutrients through farmland.    

Throughout the presentation, he walked the audience through the results of the monitoring work and what the findings may mean for water quality across the region.

Cwiertny also discussed the impact of bioreactors on nitrate levels found in tile water, explaining that they can significantly reduce nitrate concentrations. According to his findings, bioreactors can reduce nitrate levels by about 50 percent under the right conditions.

Early in the presentation, Cwiertny showed examples of measurements collected from tile water samples and explained what those numbers mean when analyzing runoff levels.

“You might get some sticker shock at first, but it’s not actually a large load,” Cwiertny said. “Because the water volume is small, the higher concentration doesn’t translate into a major concern.”

He explained that farm tile lines and drainage districts continue to be a significant source of nitrate runoff in Iowa. 

However, he also noted that bioreactors have shown promise in helping reduce nitrate levels, particularly later in the growing season when conditions allow them to operate more effectively.

Phosphorus levels were generally low in the samples that were tested and were not considered a major concern based on the monitoring results. Bacteria, including E. coli, was detected in some tile water samples, though only a small number of readings showed higher levels.

The presentation also covered pesticides that were detected in tile water. Insecticides such as clothianidin and thiamethoxam were frequently found in the samples. 

According to Cwiertny, higher concentrations of these chemicals in certain areas could pose risks to aquatic life, particularly in locations where sandy soil allows the chemicals to move more easily through the ground and into water systems.

Fungicides were also detected during the monitoring process but were found less frequently and generally at lower levels. 

Atrazine and metolachlor were found more often in the samples, which Cwiertny said could be linked to both current agricultural use and chemicals that remain in the soil from past applications.

Later in the presentation, Cwiertny discussed PFAS (per- and polyfluoroalkyl substances), which are often referred to as “forever chemicals.” PFAS were detected in some drainage samples collected in 2024. However, when samples were collected again in 2025, the same trend was not observed.

Cwiertny said he is still unsure why PFAS levels appeared higher in 2024 but were not seen at the same levels the following year. While reviewing the results, he suggested that the chemicals may have been linked to containers used to store or handle agricultural chemicals rather than a single specific application.

Throughout the presentation, Cwiertny emphasized the importance of continuing to gather data and monitor environmental conditions across the state.

Towards the end, he encouraged the audience to support increased testing and monitoring efforts, noting that limited funding has made it difficult for researchers to fully study soil, water and air contamination across Iowa.

“We need to start by gathering more data, because that’s where the process begins,” Cwiertny said. “We also need to keep investing in monitoring so we can determine whether this is actually a problem or confirm that it isn’t.”

Cwiertny added that increased testing of soil and air contamination could help communities in counties such as Muscatine, Scott, Washington and Cedar better understand potential risks to public health and the surrounding environment.