The DNR investigated for manure runoff into the Little Sioux River from northern Dickinson County after a complaint to the Spencer DNR field office Thursday.
DNR environmental specialists traced the runoff to an open feedlot owned by Troy Ahrenstorff located about two miles northeast of Lake Park.
Ammonia levels were about 150 parts per million (ppm) where concentrated runoff entered the West Fork of the Little Sioux River. The ammonia levels downstream one and a half miles were remarkably better at less than one ppm, said Bryon Whiting, a specialist at the Spencer office.
Although fish kills commonly occur at about 8 ppm of ammonia, the DNR investigators did not observe any dead fish. However, stream levels were high and may have washed any dead fish downstream.
The DNR will consider appropriate legal action for water quality violations pending the test results from water samples sent to a laboratory.