Assessment Comments
Assessment is based on results of a fish kill investigation in August 2008.
Basis for Assessment
SUMMARY: The Class B(LW) (aquatic life) uses are assessed (evaluated) as "partially supported" based on results of a fish kill investigation in August 2008.
EXPLANATION: The kill occurred on or before August 20, 2008. The kill affected 76,292 fish along 2.5 miles of the East Fork of the Wapsipinicon River. The value of the fish was estimated to be $40,053.15. No cause for the kill was identified. Water samples were collected at the time of the kill that ruled out livestock manure as the source of the kill.
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 (2006-2009) 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 2010 Integrated Report.
