Iowa's 2024 list of impaired waters was only partially approved by the EPA who said the state needs to add seven additional water segments to the list. (Photo by Cami Koons/Iowa Capital Dispatch)
The U.S. Environmental Protection Agency, after rejecting a portion of Iowa's 2024 list of impaired water segments, is now seeking public comment on decision to add seven water segments to the list.
Under the Clean Water Act, states are required to assess surface-water quality and submit a report to the EPA every two years with a list of its impaired water bodies.
The Iowa Department of Natural Resources submitted the 2024 Water Quality Assessment to the EPA in the spring and classified more than 700 water segments as impaired.
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EPA said in its recent letter to the state that the list only "partially meets" the requirements under section 303(d) of the Clean Water Act, which authorizes the EPA to help states list and develop water improvement plans for impaired waters.
Impaired waters have an identified pollutant that exceeds water quality standards and require a water improvement plan, known as a Total Maximum Daily Load or TMDL.
The TMDL is prepared by the state, and approved by EPA, for each impaired water segment and then all contributing polluters are allocated a share of the allowable load. This determines the pollutant reduction needed to meet water quality standards.
The EPA identified one segment on the Cedar River, two segments on the Des Moines River, two segments on the Iowa River, one segment on the Raccoon River and one segment on the South Skunk River as exceeding the nitrate and nitrate plus nitrite water quality standards associated with the drinking water use.
The letter from the EPA said these segments need to be on the impaired water list because of their levels of nitrate and nitrite, which have a "known toxicity."
The EPA said it asked Iowa, in a previous public comment, to "revise" its assessment of nitrogen, nitrate, nitrite and nitrate plus nitrite, but the comments were, "not adequately addressed by the state."
"Iowa DNR has not revised its assessment of these parameters to adequately address them as pollutants with toxic effects or given reasonable consideration of the endpoints and adverse effects being considered," the letter said.
The DNR responded to the public comment in May 2024, and said it would not change its methodology because, "the EPA has provided no new scientific evidence nor any new federal regulation in support of such a significant policy change."
A spokesperson for Iowa DNR said the department is reviewing the latest information provided in the EPA announcement, and did not offer further comment.
With the EPA's additions, the 2024 list has 712 impaired water segments.
Iowa also delisted 84 impaired water segments that now meet water quality standards, or have an EPA approved TMDL. The EPA approved these 84 delistings and rationals.