Assessment Comments
Assessment remains based on an IDNR investigation of a fish kill in August 2002.
Basis for Assessment
[Note: Prior to the current (2008) Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), this segment is now presumptively designated for Class A1 (primary contact recreation) uses. The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses). Thus, for the current (2008) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses are "not assessed" due to the lack of information upon which to base an assessment. The Class B(WW2) aquatic life uses remain assessed (monitored) as “partially supported" due to occurrence of a fish kill in August 2002. This kill is believed to have been caused by animal waste.
EXPLANATION: The fish kill occurred on August 24, 2002, near the intersection of 255th Avenue and 310th Street; the kill was localized to an approximately 40-meter segment of stream; approximately 100 fish were killed. The kill was believed to be caused by manure.
According to IDNR’s 2006 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 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. Thus, because this kill occurred within the 2002-2004 assessment period, and because this kill was potentially related to a pollutant impact, this stream segment was assessed (monitored) as "partially supported" and placed in Category 5b of Iowa's 2006 Integrated Report. This segment remains in Category 5b of Iowa's 2008 Integrarted Report.
