IEC Statement on EPA Rescission of 2024 Impaired Waters List Disapproval

EPA Rescinds Disapproval of Nitrate Impairments: What it Means and Why it Matters 

On July 11, 2025, EPA issued a letter to the Iowa Department of Natural Resources rescinding its disapproval of the state’s 2024 impaired waters list. This unprecedented action means that major rivers in Iowa are not treated as exceeding the nitrate standard for purposes of the Clean Water Act. 

What is the Impaired Waters List? 

Under the Clean Water Act, every state must adopt water quality standards that define how it would like to use its waters and the pollution levels that would prevent those uses. When a water does not meet the standards and is too dirty for one of its intended uses, it is “impaired.” Section 303(d) of the Clean Water Act requires states to submit a list to EPA once every two years identifying impaired waters that need a plan to reduce pollution. EPA must approve or disapprove the list. Iowa DNR submitted its list in 2024 with 705 impairments. 

States must develop a water improvement plan for each waterbody on the impaired waters list and submit them for EPA approval. The plans must identify sources of pollution and the amount of pollution reduction needed to meet the water quality standard and protect the designated uses. The reductions are incorporated into permits for point sources, such as wastewater treatment facilities, but are not required for nonpoint sources, such as agriculture. 

Nitrate Impairments 

EPA adopted a drinking water standard of 10 mg/L nitrate-nitrogen (nitrogen mass in nitrate ions) to prevent against blue baby syndrome, a condition in which infants’ blood oxygen levels drop. Drinking water providers must notify all customers if the water they deliver ever exceeds 10 mg/L. 

Iowa DNR classified some waters in the state as drinking water sources because cities use them to provide Iowans with drinking water. 96% of drinking water providers in Iowa do not have a treatment system to remove nitrate. (Des Moines Water Works is a notable exception, with one of the largest nitrate removal facilities in the world.) 

The 2024 Impaired Waters List 

Iowa DNR considered data from 2020-2022 to evaluate whether drinking water sources met the nitrate standard for the 2024 impaired waters list. IEC and other groups argued that this short-term look was not representative of water quality because it was too narrow and included drought years, which were unusually low nitrate concentrations. DNR concluded that, because the standards were rarely exceeded, the drinking water standard was met. 

EPA disagreed with DNR’s decision not to include nitrate impairments because drinking water sources did exceed nitrate in some instances. EPA noted that nitrate can have toxic effects, not just result in long-term (chronic) health problems. DNR disagreed, arguing that EPA had not listed nitrate as toxic. EPA decided to list the waters despite DNR’s objection. 

In May 2025, DNR talked with EPA and sent documents from the time the state adopted its nitrate standard to protect drinking water. In July, EPA sent a letter rescinding its disapproval and removing the waters impaired for high nitrate. 

IEC's Response

Statement from IEC Water Program Director Colleen Fowle: 

"The health risks of nitrate in our drinking water are significant, and Iowans are living with these impacts every day: birth defects, bladder and kidney cancer, thyroid disease, and more. Drinking water utilities around the state have struggled to ensure people receive water safe for their families. This summer in particular has provided a clear picture of the consequences of high nitrate in our drinking water sources.   

"Iowans across the state have been concerned about nitrate in drinking water on all the rivers that EPA has decided to remove from the impaired waters list. All have regularly exceeded the drinking water standard, but not all the cities relying on them have treatment systems to remove nitrate. 

"DNR’s proposal to remove drinking water impairments from the list was based on a short-term look at nitrate during drought years. But nitrate concentrations in our waterways are weather-dependent, and only a long-term look can capture that variability. Looking at only a few years makes no sense for pollutants that can differ from year to year based on streamflow. The long-term data show that safe drinking water is at risk. That is precisely what the water quality standard is meant to protect and the reason why these waters need to be listed as impaired."

Statement from Michael Schmidt, General Counsel, Iowa Environmental Council:

"Efforts to de-list Iowa waterbodies for nitrate are clearly misguided. This action undermines the public process and the public trust in the agencies charged with keeping our water clean. The public already had opportunity to comment and overwhelmingly supported the listing that reflected real-life conditions in these rivers. 

"We call on EPA and DNR to engage in a public process and bring Iowans together to address nitrate concerns that threaten the health and economic wellbeing of people across Iowa, rather than taking action behind closed doors. EPA’s unprecedented rescission ignores the challenges Iowans face in protecting a critical public health resource — our drinking water."

Timeline 

March 14, 2024: Iowa DNR released draft impaired waters list for comment 

April 2024: IEC and others comment on draft list 

May 3, 2024: DNR responds to comments and submits impaired waters list to EPA 

November 13, 2024: EPA issues partial disapproval of DNR impaired waters list, saying DNR needs to include nitrate impairments on the Des Moines, Raccoon, Cedar, and Iowa Rivers 

December 13, 2024: DNR, IEC, and others comment on the EPA action 

December 30, 2024: EPA takes final action to list the waters 

May 2, 2025: DNR talks to EPA about the nitrate listings, then emails two documents related to the original adoption of Iowa's nitrate water quality standard 

July 11, 2025: EPA Region 7 sends a letter to DNR rescinding the disapproval from December, removing the nitrate impairments