Assessment Comments
Assessment remains based on the results of an IDNR investigation of a fish kill that occurred in July 2001.
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 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), 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 (2010) 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 are "not assessed" due to the lack of information upon which to base an assessment. The presumptive Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" based on a report of a fish kill in July 2001. Due to the absence of kills subsequent to that kill, this assessment segment was moved from Category 4d (impaired but TMDL not required) to Category 3b (water in need of further investigation) for Iowa's 2006 Integrated Reporting cycle; the water remains in IR Catetgory 3b for the 2008 IR cycle.
EXPLANATION: The aquatic life uses remain assessed as "partially supported" due to occurrence of a fish kill. A fish kill occurred on this stream segment on July 23, 2001. The kill affected approximately 4 miles of Simpson Creek in Sections 16, 17, 21, 22, and 27 of T95N, R11W, Chickasaw Co. The kill was caused by discharge of hog manure; the responsible party was identified and restitution was sought. An estimated 32,700 fish were killed.
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. 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 where it remains for the 2010 Integrated Report.
