Big Lake (incl Gilbert's Pond) IA 06-WEM-1712

The Class B(LW) (aquatic life) uses for Big Lake are assessed (evaluated) as “partially supported” due to a fish kill in 2012. A fish kill occurred at Big Lake on or before July 18, 2012. The cause of the kill was identified as “natural/unknown.” due to An estimated 100 fish were killed. According to the DNR investigation, an unspecified number of fish killed and the cause was attributed to high temperatures and low rainfall.According to DNR’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 (2012-2016) 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 DNR 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 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 2018 Integrated Report.

Fish consumption uses remain "not assessed" (IR 3a) due to the lack of fish contaminant monitoring in this assessment segment.