East Fork Des Moines River IA 04-EDM-972

The occurrence of a fish kill in February 2004 suggested that the Class B(WW1) aquatic life uses should remain assessed (evaluated) as "partially supported". This kill occurred on or before February 10, 2004; the kill was attributed to natural causes (winterkill). An estimated 100 fish were killed. No information on the species killed was provided; no estimate of the value of the fish killed was provided. The kill affected approximately 10 miles of river. According to the DNR investigation, dead fish were observed at three riffle sites. Dissolved oxygen readings on February 10th were extremely low (less than 1ppm) at all the riffle sites (Patterson Recreation Area, Plum Creek Dam, and Veteran’s Park). The continuance of the IR Category 2b listing is based on DNR's 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 DNR 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.

According to Iowa DNR’s assessment/listing methodology, any IR 2b or 3b fish kills that occurred more than 10 years ago will be moved to IR Category 3a (not assessed); therefore, the potential impairment based on the 2004 fish kill was moved from 3b to 3a for the current (2018) IR cycle.

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S. EPA/DNR fish contaminant (RAFT) monitoring near Algona in 2008 and 2016. The tissue plug samples from three northern pike in 2016 had low levels of mercury. Levels of mercury were 0.120 ppm (sd = 0.066, max = 0.180). The level of mercury in the 2008 composite sample of walleye fillets was 0.14 ppm. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses. The fish contaminant data generated from the 2008 and 2016 fish tissue sampling conducted at this river show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.