The Class B(WW-2) (aquatic life) uses are assessed (monitored) as "partially supported" (IR 4d) due to the occurrence of a fish kill on or before October 9, 2017. Approximately 60,278 fish were killed over 6.89 miles of stream. The value of the fish was reported as $19,416.15 and the investigation cost was $2,296.29. The cause of the kill was identified as animal waste from a open feedlot at a dairy farm. The fish kill originated Unnamed Tributary to Hickory Creek IA 01-NMQ-3050 and traveled to this segment. The following comments are summarized from the Iowa DNR fish kill investigation:

Ammonia toxicity associated with an open dairy feed lot originating in Section 11, T89N, R2W, pending water sample analysis results.

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 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 is identified, and the cause is either known, or suspected, to be a “pollutant”, the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing. Fish kills attributed to a pollutant, but where a source of the pollutant was not identified and/or where enforcement actions were not taken against the responsible party, will be placed into Integrated Report subcategory 5b. The intent of placing these waterbodies into Category 5 is not to necessarily require a TMDL but to keep the impairment highlighted due to the potential for similar future kills from the unaddressed causes and/or sources. If, however, a consent order has been issued to the party responsible for the kill and monetary restitution has been sought for the fish killed, the affected waterbody will be placed in IR Category 4d (impaired but TMDL not required). Iowa DNR sought and received restitution for the value of the fish killed and the cost of the fish kill investigation. Thus, this assessment segment is placed in Category 4d of Iowa’s 2016 Integrated Report (=303(d) list).

The Class B(WW2) aquatic life uses remain assessed (evaluated) as “partially supporting” based on data collected in 1999 and 2008 as part of the DNR/SHL stream biocriteria project. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 1999 FIBI score was 37 (fair) and the BMIBI score was 52 (fair). The 2008 FIBI score was 42 (fair) and the BMIBI score was 66 (good). The aquatic life use support was assessed (evaluated) as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The riffle habitat FIBI BIC for this ecoregion is 65 and the natural substrate BMIBI BIC for this ecoregion is 70. This segment passed the FIBI BIC 0/2 times and passed the BMIBI BIC 0/2 times in the last 18 years.

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 DNR assessment methodology. DNR now requires a segment have two or more biological samples collected from the segment in multiple years over a five-year period to be considered “monitored”. This segment had multiple samples collected in the previous 18 years (1999-2016); however, the samples were not collected during a five-year period. According to DNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). DNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation). However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b-t and remains on Iowa’s Section 303(d) list of impaired waters.