Assessment Comments
Assessment is based on results of a fish kill investigation on August 3, 2006.
Basis for Assessment
SUMMARY: The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” due to a fish kill in August 2006. The kill was attributed to natural causes. This impairment is appropriate for Category 3b of Iowa’s 2008 Integrated Report. Fish consumption uses are "not assessed" due to a lack of fish tissue monitoring at this lake. The source of data for this assessment is results of a fish kill investigation on August 3, 2006.
EXPLANATION: The fish kill occurred on or before August 3, 2006 and was attributed to natural causes (high temperatures and low dissolved oxygen). An estimated 20 fish were killed including small number of bass, northern and yellow bass. Anglers have observed live bluegill in the lake. No estimate of the value of the fish killed was provided.
According to Iowa’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., winter kill), 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.
