New Iowa law prompts city ordinance updates

Faced with 2024 legislation the Iowa General Assembly approved restricting cities and counties from setting their own regulations on topsoil and surface stormwater runoff, local officials have found themselves reworking ordinances to comply with new standards applying to construction sites. 

The measure’s House of Representatives Floor Manager, State Rep. Jon Dunwell, R-Newton, said Senate File 455 (SF455) “brings significant value to Iowa by streamlining stormwater and topsoil regulations at construction sites.” 

He continued:  

“A key advantage of this legislation is its standardization of rules, which eliminates overly restrictive local regulations that can inflate home-building costs by thousands of dollars. By reducing these unnecessary expenses, the law seeks to enhance housing affordability, tackling a pressing issue for Iowans who face barriers to homeownership,” Dunwell said. “This approach ensures that the financial weight of excessive regulatory demands doesn’t disproportionately burden new homeowners, striking a practical balance between development costs and community interests.” 

The measure prohibits local topsoil and stormwater regulations at construction sites from being more restrictive than National Pollutant Discharge Elimination System (NPDES) requirements. Among the new law’s provisions, counties and cities can: 

• “adopt or enforce an ordinance, motion, resolution, or amendment that regulates storm water runoff at a construction site for five- to 100-year rainfall events only if the storm water flow rate is not more restrictive than the existing flow rate of a five-year rainfall event, with all runoff rates based on site conditions at the time construction commences.
• “adopt or enforce an ordinance, motion, resolution, or amendment that regulates storm water runoff from upstream properties adjacent to a construction site if the runoff is allowed to pass through downstream storm water basins at the same flow rates as off-site storm water runoff entering the construction site.
• “impose storm water runoff requirements that are more restrictive than what is allowed or required by the (Iowa Department of Natural Resources) if the county or city pays for all study, design, and engineering costs associated with implementing the storm water runoff requirement; pays for one-half of any equipment or practices required for a property owner to comply with the requirement; pays the property owner the fair market value of any property or easement taken to impose the requirement; and pays the costs incurred without imposing a special assessment or otherwise recovering the costs solely from the property owner for the costs attributable to the county or city.”
• “impose a storm water runoff requirement that is more restrictive than established in federal or State law if the county or city and the owner of the affected property agree to the requirement.”

Beyond cost savings, Dunwell said, the measure offers flexibility for local governments to address unique stormwater challenges. 

“This provision prevents a one-size-fits-all increase in construction expenses across the state while preserving some local autonomy, ensuring the legislation’s cost-saving goals remain intact without compromising the ability to respond to regional needs,” he said. “For Iowa, this law represents a strategic step toward affordable housing and sensible regulation.” 

Zooming in on Des Moines 

The Des Moines City Council voted in late January 2025 to update its 2021 stormwater ordinance, which was approved in the wake of 2018 and 2020 flash floods, to be in accordance with SF455. The state’s largest city will continue efforts to mitigate flooding risks through the construction of stormwater detention basins and a program that provides a 50% match up to $2,000 for homeowners and businesses that install stormwater best management practices. Other cities across the state have updated or are updating their ordinances. 

Alan Kemp, executive director of the Iowa League of Cities, said in interview last year with the Business Record, a Des Moines publication, that SF455, along with other mandates imposed on localities, represents “a one-size-fits-all approach, which the league and city officials argue doesn’t really work in a state in which you have 940 cities with populations as small as 12 on up to 220,000. And they all have unique issues based on their geography, their demographic makeup [and] their commercial businesses.”  

Kemp attributed Iowa’s recent actions to diminish home rule to the rise of larger majorities by one party or the other in legislatures across the nation.  

“You get a completely different political environment if you’re looking at a 51-49 (party split) chamber because suddenly things are a little tight, and leadership has to work together to ensure something gets passed,” Kemp said in the April 2024 interview.  

The Iowa Emergency Management Association, Iowa Rivers Revival, Iowa Section of the American Water Works Association, Iowa Association of Water Agencies, Conservation Districts of Iowa, Iowa Association of Building Officials, Iowa Section of the American Society of Civil Engineers, Iowa Stormwater Education Partnership (ISWEP), Iowa Engineering Society and the Iowa Division of the Izaak Walton League were registered against SF455. Two groups — the Home Builders Association of Iowa and Iowa Real Estate Developers Association — registered in support of the bill. 

Dr. Loulou Dickey, ISWEP executive director, said she believes bill supporters were well-intentioned.  

“There was a lot of talk about affordable housing. I think they were addressing the idea that there was some overreach or over-regulation going on,” she said. “I would like to see more collaboration rather than a prescriptive one-size-fits-all approach.” 

Noting that opinions about regulatory overreach are a subjective matter, Dickey added the Iowa stormwater standards are based on “good science and good engineering.” 

“We all want to make sure that we're protecting our water resources and that we're not causing problems for folks downstream from us,” she said. “What we mostly hear is that communities are just trying to  …make sure they are doing their best to manage stormwater in a sustainable and responsible way while complying with the new law.” 

Dickey expressed concerns about proposed legislation that would “potentially add more complexity and challenges” by limiting how cities can collect utility fees – which would constrain budgets for infrastructure maintenance and construction – or could impact stormwater and erosion control by changing landscaping regulations. 

“The more that these types of laws are passed, it's just going to make it increasingly challenging for cities to sustainably manage their stormwater,” she said. 

Striking a balance between protecting the environment while still encouraging growth requires planning the most-effective investments in runoff prevention, environmental resilience and sustainable practices, Dickey said. 

More than 85% of Iowa — roughly 30 million acres, is farmland mostly dedicated to corn and soybean production. Soil conditions and topography vary dramatically for the state situated between the Missouri and Mississippi rivers. 

“Sometimes what seems affordable in the short term is actually not affordable in the long term. Especially in Iowa, our soil is so precious and valuable. It takes hundreds, if not thousands, of years to form, so we need to make sure we’re taking that into account,” she said. “When we're building in urban areas, we should think about how we protect that soil there.” 

How other states compare 

SF455 appears to be unusual as examples to rollback existing regulations are rare. 

In Maryland, regulations aimed at reducing stormwater runoff at construction sites were enacted in 2007 and took effect in May 2010. The Bay Journal reported at the time that “last-minute revisions” allowed developers more leeway to exempt their projects from the act’s restrictions after “debates raged as the Maryland Department of the Environment worked with local jurisdictions to finalize details and put the regulations into effect.” 

Ultimately, legislators approved emergency regulations to extend the grandfather period, giving projects until May 2013 to receive full approval and setting May 2017 for completion. A Maryland Department of Environment spokesperson told the Bay Journal that the emergency regulations supplanted legislative attempts to weaken the original measure, noting they provided the possibility of a waiver for projects meeting “very specific guidelines” and did not alter technical standards. 

In North Carolina, then-Gov. Roy Cooper vetoed an attempt to weaken local governments’ ability to regulate stormwater runoff from developments that had been built before the state enacted stricter runoff laws. That measure, which was a regulatory reform act, was passed during a one-day special session.  

In his veto message, Cooper stated, “We should make it easier, not harder, for state and local governments to protect water quality, whether through stormwater safeguards or by giving public health departments the ability to revisit wastewater permits if needed. Rolling back ways to protect water quality is dangerous.”