A Polk County judge has ordered state environmental regulators to reconsider a nutrient management plan that paved the way for establishing a large cattle feedlot in northeast Iowa near a cold-water trout stream, saying parts of the plan contain "illogical interpretations and applications."

The ruling gives environmentalists a win against the project, which they say threatens Bloody Run Creek. The stream is listed among state-designated Outstanding Iowa Waters.

District Judge Scott Rosenberg on Friday reversed the Iowa Department of Natural Resource's 2021 approval of the nutrient management plan for the 11,600-head Supreme Beef operation near Monona.

"While the record is a mixture of good interpretation and application of the law," Rosenberg wrote in the ruling, the nutrient management plan "in question is … marked with illogical interpretations and applications."

Environmentalists say area's geology adds to stream's vulnerability

The Sierra Club of Iowa and the Iowa State Council of Trout Unlimited challenged the DNR's approval of the plan, suing both the agency and Supreme Beef.

The groups claimed the plan underestimated the amount of nitrogen and phosphorus from the application of the facility's manure to surrounding cropland, putting Bloody Run Creek at risk of being polluted.

Previously: Iowa Sierra Club can continue lawsuit against state DNR over cattle feedlot near trout stream

The Supreme Beef feedlot sits near the headwaters of Bloody Run in an area of karst topography. Environmentalists say the fractured, porous limestone below the soil there allows groundwater to move quickly, carrying contaminants to surface waters and aquifers.

Nitrogen and phosphorus are needed to grow crops, but the nutrients are considered pollutants when they move from fields into Iowa's lakes, rivers and streams.

"From the very beginning, the Department of Natural Resources had to contort its rules in order to approve the Supreme Beef nutrient management plan," the Sierra Club said online.

DNR says it won't appeal for now

The environmental groups said the DNR could appeal the ruling to the Iowa Supreme Court, ask the judge to reconsider or void the nutrient management plan and consider a new one.

The DNR said Tuesday it "does not anticipate an appeal at this time" and will ask for another nutrient management plan.

In his ruling, Rosenberg agreed with the state's determination that the operation is an open feedlot, and with the calculations used to assess runoff of pollutants.

But he disagreed with other parts of Supreme Beef's nutrient plan, including the company's methods for determining the amount and nutrient content of manure that the cattle would generate in the operation.

His ruling cited Supreme Beef's use of a manure sample from Upper Iowa Beef, a beef processing plant in Lime Springs, to calculate the nitrogen and phosphorous values.

The DNR claims Upper Iowa Beef "is an open feedlot like Supreme Beef," but Rosenberg wrote that the plant "is a cattle-slaughtering operation, not a feedlot."

Additionally, the DNR "illogically interpreted the law and applied the law to the analysis of ephemeral gully erosion" and lacked information about maintaining and operating a manure storage facility.

Sierra Club attorney: 'We'll make them do it right'

Sierra Club attorney Wally Taylor said Tuesday the ruling will help reinforce the environmental groups' arguments if the state decides to reconsider Supreme Beef's manure management plan.

More: Iowa company will convert cow manure into natural gas. But is it an environmental asset or hazard?

Taylor said Supreme Beef had failed to modify its manure management system, which originally was geared to plans by a larger group of developers to use an anaerobic digester to convert methane from the manure into salable natural gas. That plan failed to materialize after the group ran into construction and financial trouble.

The company's current owners ditched the digester and focused on feeding cattle.

"They didn't change the manure management setup," which "doesn't comply with open feedlot regulations," Taylor said. The manure management system is more like what's required for a confined animal feeding operation, which "would have been prohibited" in a karst area, he said.

"We'll make them do it right," Taylor said. "But I'm not sure they can."

Donnelle Eller covers agriculture, the environment and energy for the Register. Reach her at deller@registermedia.com or 515-284-8457.

This article originally appeared on Des Moines Register: Judge: Parts of DNR decision allowing Iowa cattle feedlot 'illogical'