Assessment Comments
Assessment is based on results of a fish kill investigation in May 2006.
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 are assessed (evaluated) as "partially supported" based on results of a fish kill investigation in May 2006.
EXPLANATION: The Class B(WW2) aquatic life uses are 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 7557 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/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 (2004-2007) 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.” Such assessments, although suitable for Section 305(b) reporting, lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (IR Category 5). Waterbodies affected by such fish kills will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation. Thus, this assessment segment will be placed in Category 3b of Iowa’s 2008 Integrated Report.
