Assessment Comments
Assessment remains based on results of an IDNR investigation of a fish kill in August 1999.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was classified only for general uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, this segment is now presumptively designated for Class A1 (primary contact recreation) uses and for Class B(WW1) aquatic life uses. According to the Iowa Water Quality Standards, all perennial rivers and streams and all intermittent streams with perennial pools that are not specifically listed in the Iowa surface water classification are designated as Class A1 and Class B(WW1) waters. Thus, for the current (2012) assessment, perennial flow is presumed, and the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW1) water quality criteria.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment. The presumptive Class B(WW1) aquatic life uses are considered “not assessed”. For the 2006 through 2010 cycles, this segment was assessed (evaluated) as "partially supported" due to the report of a fish kill in August 1999. Because no additional kills have been reported for this stream for over 10 years, this segment is being moved to IR Category 3a (not assessed) for the 2012 cycle.
EXPLANATION: A fish kill occurred in this segment near Ainsworth in August 1999. The kill was attributed to sewage from the Ainsworth municipal wastewater lagoon. An estimated 4,500 fish were killed (see assessment for the 2000 reporting cycle for more information). The party responsible for the kill was identified, and restitution was sought.
According to DNR's assessment methodology for Section 305(b) reporting, occurrence of a single pollution-caused fish kill during an assessment period indicates "partial support" of the aquatic life uses. If, however, a consent order has been issued to the party responsible for the kill and monetary restitution has been sought for the fish killed, the affected waterbody should be placed in IR Category 4d (impaired but TMDL not required). Thus, this assessment segment was placed into Category 4d of Iowa's 2004 Integrated Report. Also, IDNR considers IR 4d fish kill waters with no subsequent kills reported in at least five year subsequent to the kill as appropriate for movement from IR Category 4d to either categories 2b or 3b (i.e., Iowa’s list of waters in need of further investigation). Thus, this assessment segment was moved to Category 3b of Iowa’s 2006 Integrated Report and remained in Category 3b through Iowa's 2010 Integrated Reporting cycle. Because no additional kills have been reported for this stream for over 10 years, this segment is being moved to IR Category 3a (not assessed) for the 2012 cycle.
