(Ames, Iowa)  – The Iowa Department of Natural Resources says the City of Audubon has agreed to pay an $8,000 fine for repeatedly expelling too much ammonia nitrogen in its wastewater that flows to the East Nishnabotna River. The Iowa Capital Dispatch reports, according to a recent DNR order, Audubon violated its ammonia limits in nearly every month of 2021 and 2022 and in several months of 2023.

Elevated levels of ammonia can be toxic to fish and other aquatic life and can deplete oxygen in water. The city has said its pollution woes were the result of large amounts of contaminants from a truck stop that pipes its wastewater to the city’s treatment facility. Waspy’s Truck Stop opened about six years ago and has a truck wash that is used to clean the insides of animal trailers. That debris was believed to be the source of the excessive ammonia levels in Audubon’s treated wastewater. The DNR also fined Waspy’s $8,000 this year and said it had violated its pollutant limits — for ammonia nitrogen, waste solids, oil and grease — more than 500 times.

The truck stop has installed barriers to collect the manure and help prevent it from being discharged to the treatment facility. Audubon’s public works director was not immediately available to comment for this article, but he has said the situation was improving. The DNR order noted that Audubon was warned multiple times that it was exceeding its contaminant limits but that it failed to expeditiously remedy the problem.

Wastewater from Audubon flows into a creek that goes to the East Nishnabotna River. (Photo by Jared Strong/Iowa Capital Dispatch)

Treated wastewater from the city flows through a creek to the East Nishnabotna, which was polluted downstream in March by a large fertilizer spill near Red Oak. The spill killed nearly all the fish and other aquatic life in about 60 miles of the East Nishnabotna and Nishnabotna rivers.