Assessment Comments
Assessment remains based on results of a fish kill investigation on April 19, 2006.
Basis for Assessment
SUMMARY: The Class A1 uses remain "not assessed" due to the lack of water quality information upon which to base an assessment. The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supporting" based on occurrence of a fish kill in 2006. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this assessment segment.
EXPLANATION: The Class B(WW1) (aquatic life) uses remain assessed (evaluated) as "partially supported" due to a fish kill in April of 2006. The kill occurred on or before April 19, 2006; no cause of the kill was identified. Approximately 24 dead fish were observed in a pool on the Wapsipinicon River. The species of fish could not be identified due to the level of decay. Levels of ammonia in the water were below the detection limit. Dissolved oxygen concentrations were greater than 10 mg/L and the temperature was 48 ○F. No estimate of the value of the fish was developed.
This is the same assessment as that developed for the 2008 and 2010 assessment/listing cycles. The continuance of the IR Category 3b listing is based on IDNR's 2010 assessment methodology that states the following: 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. Thus, this assessment segment will remain in Category 3b of Iowa’s 2012 Integrated Report.
