The Raccoon River on June 13, 2025 as it weaves past downtown Des Moines and towards Gray’s Lake Park. (Photo by Cami Koons/Iowa Capital Dispatch)
Central Iowa Water Works’ long-range plans will increase water treatment capacity by 25%, and once in place would prevent water conservation orders like the lawn watering ban currently in place.
In the meantime, CIWW leadership said the lawn watering ban will remain in place as it has reduced demand and allowed the system to remove the “near historic” levels of nitrate from the Des Moines and Raccoon rivers.
Tami Madsen, CIWW executive director, speaking at a press conference Tuesday, emphasized that the regional water supply is dealing with a water quality issue and not a water quantity issue.
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The system pulls water from the Des Moines and Raccoon rivers, and when necessary, treats the water for nitrate concentrations that exceed the U.S. Environmental Protection Agency’s drinking water concentration limit of 10 milligrams per liter. According to CIWW the rivers had concentrations as high as 17 mg/l and despite running the nitrate removal systems at full capacity for nearly 60 days, water leaving the facility was in danger of exceeding the federal limits.
CIWW issued a mandatory lawn watering ban June 12. Madsen said lawn watering accounts for 40% of demand, so stopping that use is the “fastest, most efficient way to reduce demand.”
Ted Corrigan, the CEO and general manager at Des Moines Water Works, which is part of the CIWW system, said the last time nitrate levels in both the Des Moines and Raccoon rivers were this high was in 2013.
Corrigan said there is a trend of higher nitrate concentrations when there is a year of average precipitation following periods of drought, as the region has seen the past several years.
Corrigan said rain in the Des Moines area would help the system by reducing demand and adding fresh water to the rivers. But, he said, rain up the watershed could have a negative effect by flushing more nutrients through farm tile lines, off of fields and into the river.
He said the situation is “very dynamic” and therefore it is difficult to say when the lawn watering ban might be lifted, but he expects levels in the rivers will decline in the next two to three weeks.
Corrigan said outgoing water has remained below the EPA limit, thanks to customers in the system who have complied with the lawn watering ban.
“That is entirely due to the fact that the community has responded so well to our request,” Corrigan said. “Without that we would have violated the nitrate standard.”
Long-term plan will add significant treatment capacity
Central Iowa Water Works is a regional water production authority founded by 12 utility and water entities in central Iowa. It serves more than 600,000 customers.
Christina Murphy, West Des Moines Water Works’ general manager, said the CIWW has been planning capacity expansions that will help to treat water for nitrate, and other contaminants.
The plans include doubling the Saylorville Water Treatment Plant, which would add an additional 10 million gallons each day, expanding the City of Grimes Water Treatment Plants and constructing a 12-million-gallon, per day, treatment plant to the Des Moines metro’s west side. All of these facilities will have the ability to treat nitrates, according to Murphy.
“We’re planning for the future — we’re not talking about just nitrates, we’re talking about production capacity that can treat not only nitrates but emerging contaminants,” Murphy said.
Additionally, two aquifer storage facilities within the CIWW sphere are under construction and a third is being designed, which Murphy said will also add to treated water capacity.
All told, the expansions will add 34.2 million gallons per day of treatment capacity.
“If we had that capacity online today, I think it’s safe to say we wouldn’t have to be in the stage 3 position,” Murphy said, referencing the water conservation stage of banning lawn watering.
Corrigan said the length of the current ban, which has also stopped spraygrounds and splash pads around the city, will likely be measured in terms of weeks instead of days.
“We’re gonna need your continued support,” he said.