Assessment Comments
Assessment is based on results of an IDNR investigation of a fish kill in August 2004.
Basis for Assessment
SUMMARY: The general uses of this stream are assessed (monitored) as “partially supported” due to a fish kill in August 2004. Although a definitive cause of the kill was not identified, IDNR investigators hypothesized that feedlot runoff may have been involved in the kill. The party responsible for the kill was not identified. This impairment is appropriate for Category 5b of Iowa’s 2006 Integrated Report (=Section 303(d) list).
EXPLANATION: This kill occurred on or before August 25, 2004. A definitive cause of the kill was not identified. The kill began south of Marcus at a bridge on the north side of section 26 of T92N, R42W; the kill extended 5.3 miles downstream and ended in the center of Section 10 of T91N ,R42W, Cherokee County. An estimated 7,201 fish were killed; no estimate of the value of the fish killed was provided. The fish killed included non-game species (e.g., minnows, suckers, and darters) and also included approximately 2,000 stonecats (Noturus flavus). No responsible party was identified. Although a definitive cause was not identified, IDNR investigators hypothesized that runoff from nearby sheep feedlot may have caused the kill.
According to IDNR’s assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period (2002-2005) indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired”. If a cause of the kill is identified, and the cause is either known, or suspected, to be a “pollutant”, the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing. Fish kills attributed to a pollutant, but where a source of the pollutant was not identified and/or where enforcement actions were not taken against the responsible party, will be placed into Integrated Report subcategory 5b. The intent of placing these waterbodies into Category 5 is not to necessarily require a TMDL but to keep the impairment highlighted due to the potential for similar future kills from the unaddressed causes and/or sources.
