EPA confirms additions to Iowa impaired waters list

by Cami Koons, Iowa Capital Dispatch
January 13, 2025

The U.S. Environmental Protection Agency affirmed its November decision to add seven additional segments to Iowa’s list of impaired waters, following a public comment period. 

EPA announced in November it had partially approved the Iowa Department of Natural Resources’ assessment of surface water quality in the state and called for the inclusion of additional segments on the Cedar, Des Moines, Iowa and South Skunk rivers, based on measured levels of nitrate.

Per EPA documentation, a vast majority of the public comments submitted were in favor of the EPA decision. DNR, which monitors and compiles the impaired waters list every two years, per the Clean Water Act, called EPA’s assessment “illegal” since nitrate is not officially listed as a “toxic pollutant” under the Clean Water Act.

DNR director Kayla Lyon wrote in a letter to EPA that the two organizations share a goal of making Iowa’s tap water safe to drink. “It is safe,” Lyon wrote after explaining DNR’s drinking water quality standards meet the federal Safe Drinking Water Act. 

“There is legal and scientific significance to listing nitrate as a ‘Toxic Pollutant’ under the CWA, including more costs, regulatory oversight, and burdens,” Lyon wrote in the letter to EPA. “In the end, listed or not, Iowa’s drinking water must meet SDWA’s nitrate (maximum contaminant level), which it does.” 

Once a segment is designated as impaired, a total maximum daily load, or TMDL, of the excessive pollutant is established and contributing polluters are allocated a share of this load to help bring down the total concentration.

Lyon also argued EPA did not provide reasoning, data or methodology for its decision. In its comment, submitted Dec. 19, DNR requested EPA withdraw its decision to add the seven segments, or otherwise establish loads that are consistent with federal code and allow the public to review and comment on it.

“EPA’s patchwork approach to nitrate across the country violates the Administrative Procedure Act for being arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law,” Lyon said in the letter. “Some states mirror Iowa’s approach to assessing nitrate in surface drinking water sources whereas others don’t test at all … the EPA is holding Iowa to a very high standard that it does not enforce elsewhere.”

In the EPA response to DNR, the Iowa Farm Bureau Federation and the Fertilizer Institute, which all wrote comments opposing the decision, the agency acknowledged the water quality standards and assessment approaches toward nitrates “vary across states.” 

The agency points to Iowa water quality standards that say “all substances toxic or detrimental to humans” or to the water treatment process are to be limited to “nontoxic or nondetrimental concentrations.” EPA said it used this water quality standard to justify the additional segments, because water treatment facilities must use “additional treatment” to meet drinking water nitrate standards, per its own code. 

EPA said it gathered data from DNR’s own reports and public data from Des Moines Water Works, which was among several public water suppliers that submitted comments supporting the EPA decision. 

“EPA found that the existing and readily available water quality data demonstrate that the seven specified (segments) are not attaining applicable water quality standards, and the state did not provide a technically defensible rationale in its assessment,” EPA said in its response to public comments. 

EPA said it “adhered to all legally applicable requirements” in its action. 

Ted Corrigan, the CEO and general manager of Des Moines Water Works, wrote the utility servicing a fifth of Iowa’s population was supportive of the EPA decision. Corrigan noted Des Moines Water Works, which receives water from both the Raccoon and the Des Moines rivers, has had a nitrate removal facility since 1992. 

“Since that time nitrate concentrations in the river flowing past the intake at our Fleur Drive Treatment Plant have not improved,” Corrigan said. 

Corrigan said nitrate concentrations overall in the rivers continue to climb, with concentrations in the Raccoon River in 2024 among the highest the utility had seen. 

EPA said it received 83 comments about the decision, 72 of which were in support of including the additional seven segments to Iowa’s impaired water list. 

Environmental advocacy groups, including the Iowa chapter of the Sierra Club, Iowa Environmental Council and Iowa Citizens for Community Improvement were among supportive commenters. The same groups submitted a letter to EPA in the fall, urging the agency to take action on protecting drinking water sources from nitrate pollution.

A spokesperson for Iowa DNR declined to comment on the EPA decision.

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