Cedar Creek IA 04-RAC-1819

The presumptive Class B(WW-1) (aquatic life) uses are assessed (monitored) as "partially supported" due to the occurrence of a fish kill in September 2013; the kill occurred in Pocahontas County approximately 7 miles NE of Fonda. The kill occurred on or before September 16, 2013. An estimated 99,900 fish were killed over 4.8 miles of stream. The value of the fish was reported as $19,862.81; the investigation cost was $495.26. The cause of the kill was identified as a spill of animal waste from a hog confinement via an underground tile line that came from a small hog confinement/nursery that uses an earthen basin to store manure.

According to IDNR’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). Updated information shows that Iowa DNR has sought and received restitution for the value of the fish killed and costs of the IDNR fish kill investigation.  Thus, this impairment is moved from IR Category 5b to IR Category 4d for the current (2016) listing cycle.

Consistent with the assessment based on the September 2013 fish kill, the results of IDNR/SHL biological monitoring suggest that the presumptive Class B(WW1) aquatic life uses should be assessed (evaluated) as “partially supporting” based on biological data collected in 2001 and 2006 on Big Cedar Creek approximately 7 mile NNE of Fonda in Pocahontas County as part of the IDNR/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 2001 FIBI score was 48 (fair) and the BMIBI score was 47 (fair). The 2006 FIBI score was 57 (good) and the BMIBI score was 38 (fair). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The riffle site FIBI BIC for this ecoregion is 53 and the BMIBI BIC for this ecoregion is 62. This segment passed the FIBI BIC 1/2 times and passed the BMIBI BIC 0/2 times in the last 14 years.

This aquatic life assessment is now considered "evaluated" based on a change in the 2010 IDNR assessment methodology. IDNR now requires a segment have two or more biological samples collected from the segment in multiple years over a recent five-year period to be considered “monitored”. This segment had multiple samples collected in the previous 14 years (2001-2014); however, the samples were not collected during a recent five year period. Also, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). According to IDNR’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). IDNR 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).