Soldier Creek IA 04-UDM-1277

The kill occurred on or before May 24, 2006; no cause of the kill was identified. Approximately 7,557 fish were killed beginning in an unnamed tributary near Floral Ave on west side of Sec. 17, T89N, R28W (NE Fort Dodge) and extending 2.7 miles downstream in Soldier Creek ending at the Des Moines River Sec. 19, T89N,R28W. The cause of the fish kill was unknown, but was possibly due to storm drain runoff. The value of the dead fish was estimated to be $3,246.92. The investigation cost was $3,933.63.

According to IDNR’s assessment 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 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. ). Due, however, to the large number of fish killed (~7,500), the length of the kill (2.7 miles), and the lack of environmental extremes during summer 2006 that would have contributed to this kill (e.g., low stream flow and/or high water temperatures), some type of pollutant cause is suspected. Thus, this assessment was moved from Category 3b of the Iowa's 2010 Integrated Report (potentially impaired) to IR Category 5b (impaired) of Iowa’s IR.

This stream segment’s fish community was sampled on October 8, 2014, as part of the IDNR Watershed Improvement and Water Monitoring sections’ fishkill follow up monitoring program. Sampling methods described in IDNR’s fish kill follow-up protocol (Attachment 5 of Iowa’s assessment/listing methodology) were followed. Approximately 520 feet of stream were sampled using a single pass with two backpack electro fishing units. Results of this sampling show that this stream supports approximately 4,500 fish per mile compared to the Level IV ecoregion 47b average of approximately 2,310 fish per mile; 82% of the expected fish taxa for this ecoregion were sampled. For detailed results of this sampling, see https://programs.iowadnr.gov/bionet/Sites/976. The results from this follow-up sampling and comparison of these results to ecoregion averages suggest that the fish community of this stream segment is similar to or better than non-fishkill impacted streams. Although the results of the fishkill follow-up sampling lack the scientific rigor to determine whether the designated aquatic life uses are “fully supported,” the results do indicate that the stream has recovered from the May 2006 fish kill event. Thus, the assessment of aquatic life use support for this stream segment is being moved from impairment Category 5b of Iowa’s Integrated Report to Category 3a (designated use not assessed).