DNR Investigation Links Fish Kill in Dry Run Creek to Dairy Runoff

WINNESHIEK COUNTY, Iowa—A state investigation by the Iowa Department of Natural Resources has concluded that manure runoff from Dale Humpal Dairy led to a significant water quality violation in Winneshiek County, resulting in the deaths of more than 100,000 fish in Dry Run Creek and its tributary. The investigation began on March 11, 2025, after reports surfaced of a fish kill in the area. Upon arrival at the Humpal facility, DNR Environmental Specialists observed manure runoff flowing from open feedlots into a tile intake. This runoff then discharged into an unnamed tributary west of 255th Avenue, which feeds into Dry Run Creek. Field testing conducted throughout the afternoon and into the following day confirmed elevated levels of ammonia — a common indicator of manure contamination — in multiple locations downstream from the facility. At a bridge on 255th Street, the water tested positive for ammonia, and further testing downstream at 245th Avenue and under the Town Line Road bridge yielded similar results. Notably, dead fish or struggling fish were observed at the Town Line Road site. At the Highway 9 bridge near Decorah, a sample was collected at 2:40 p.m. on March 12. The field test showed ammonia presence, with a water temperature of 44°F and a pH level of 6. Laboratory tests of samples collected earlier confirmed ammonia concentrations of 10 ppm at 233rd Avenue, and 23 ppm at both a tile outlet and tile inlet upstream: levels consistent with manure runoff. The neighboring farm, which houses largely dairy cattle in confinement buildings and open feedlots, has a history of similar violations. The investigation also ruled out other potential sources of contamination. DNR Field officers systematically tested additional tile outlets and tributaries between the Humpal facility and Dry Run Creek, finding no evidence of ammonia runoff from other locations. By March 26, follow-up visits confirmed that ammonia levels had returned to normal. "I checked 255th Avenue, Town Line Road, and north of the Highway 9 bridge," noted the report. "No ammonia was detected at any of these locations." The DNR officially contacted Mr. Humpal on March 31 to share its findings. Humpal was informed that the runoff from his open feedlot had entered a tile intake and discharged into a nearby tributary, leading to the fish kill. The DNR emphasized that no other open feedlots in the area were found to be contributing to the pollution. On April 1, 2025, the DNR issued a Notice of Violation to Humpal Dairy. The violation cited runoff of open lot manure, a resulting water quality violation under Iowa Code 455B.186, and a freeboard violation in the facility's earthen basin. State regulations require that manure storage structures maintain a minimum of two feet of freeboard to prevent overflow and discharge. DNR officials found that this threshold had not been met. The Iowa Administrative Code requires surface waters to remain free from substances that settle to form sludge, cause objectionable color or odor, or create conditions toxic to human, animal, or plant life. The Humpal Dairy runoff was determined to have violated multiple provisions, particularly those concerning acute toxicity and objectionable conditions due to agricultural waste. While the DNR investigation has now concluded, the environmental and ecological damage to Dry Run Creek remains significant. The agency has not yet announced whether civil penalties or further enforcement actions will follow the issued violation.