Assessment Comments
Assessment is based on results of an IDNR investigation of a fish kill in September 2003.
Basis for Assessment
SUMMARY: The general uses of this stream are assessed (monitored) as “partially supported” due to a fish kill in September 2003. The kill was caused by animal waste from an open feedlot. The party responsible for the kill was not identified. This kill and others that occurred in smaller streams in northwest Iowa from September 11-15, 2003 were believed related to a rainfall event that followed a prolonged dry period. None of the investigations of these kills, however, suggested a specific pollutant-related cause. Thus, this impairment is appropriate for Category 5b of Iowa’s 2006 Integrated Report (=Section 303(d) list).
EXPLANATION: This kill occurred on or before September 11, 2003; the kill was attributed to animal waste from an open feedlot (animal type unknown). An estimated 101 fish were killed; except for one white sucker, the fish killed water reported to be “minnows”. No estimated value of the fish killed was provided. An estimated 3 miles of this stream was affected by the kill. No responsible party was identified. The location point for this kill is the SW ¼ of the SE ¼ of Section 19, T94N, R43W, Sioux County near Granville. According to the IDNR investigation, this stream has many feedlots along its banks. A heavy rain (5-6 inches) occurred on the day of kill, and this rain event likely flooded the stream with farm and feedlot runoff. Recent drought conditions and low stream flows likely made the fish susceptible to any kind of pollution that might have washed in from the recent rainfall.
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.
