Assessment Comments
Assessment remains based on results of a fish kill investigation in May 2006. Due to a review of the results of IDNR’s 2006 fish kill investigation, this assessment is moved from Category 3b of the 2010 Integrated Report (potentially impaired) to IR Category 5b (Section 303(d) impaired).
Basis for Assessment
[Note: Prior to the 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, 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 (2012) 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 remain "not assessed" due to the lack of information upon which to base an assessment. The Class B(WW2) aquatic life uses remain assessed (evaluated) as "partially supported" based on results of a fish kill investigation in May 2006. Due to a review of the results of IDNR’s 2006 fish kill investigation, this assessment is moved from Category 3b of the 2010 Integrated Report (potentially impaired) to IR Category 5b (Section 303(d) impaired).
EXPLANATION: The Class B(WW2) aquatic life uses remain assessed (evaluated) as "partially supported" based on results of a fish kill investigation in May 2006. The kill occurred on or before May 24, 2006; no cause of the kill was identified. Approximately 7,557 fish were killed beginning in an unnamed tributary near Floral Ave on west side of Sec. 17, T89N,R28W (NE Fort Dodge) and extending 2.7 miles downstream in Soldier Creek ending at the Des Moines River Sec. 19, T89N,R28W. The cause of the fish kill was unknown, but was possibly due to storm drain runoff. The value of the dead fish was estimated to be $3,246.92. The investigation cost was $3,933.63.
According to IDNR’s assessment 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 was not identified during the IDNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated” and will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation. ). Due, however, to the large number of fish killed (~7,500), the length of the kill (2.7 miles), and the lack of environmental extremes during summer 2006 that would have contributed to this kill (e.g., low stream flow and/or high water temperatures), some type of pollutant cause is suspected. Thus, this assessment is being moved from Category 3b of the Iowa's 2010 Integrated Report (potentially impaired) to IR Category 5b (impaired) of the 2012 IR.
