Assessment Comments
Assessment based on 2007, 2011 and 2013 IDNR/SHL biological sampling data and the results of a fish kill investigation in September 2009.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(LR) aquatic life uses. Due to changes in Iowa’s surface water classification that were approved by U.S. EPA in February 2008, this segment is now presumptively designated for Class A1 (primary contact recreation) uses. The stream remains designated for aquatic life uses (now termed Class B(WW2) aquatic life uses). Thus, for the current assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]
SUMMARY: The presumptive Class A1 (primary contact recreation) uses remain "not assessed" (IR 3a) due to the lack of information upon which to base an assessment. The Class B(WW2) aquatic life uses remain assessed (monitored) as “partially supporting” (IR 5b-v) based on both of the following: (1) results of IDNR/SHL biological monitoring conducted in 2007, 2011 and 2013 (IR 5b-v) and (2) results of a fish kill investigation in September 2009 (IR 5b).
EXPLANATION: The Class B(WW2) aquatic life uses remain assessed (monitored) as “partially supported” based on results of a fish kill investigation in September 2009. The kill occurred on September 15, 2009, and was caused by a spill of mixed pesticides from the Co-op. Approximately 17,618 fish were killed in an undefined stretch of Bailey Creek near Thornton. The value of the fish was estimated to be $8,541.66. At the time of this assessment (April 2014), there is no record of whether the DNR sought or received restitution for this fish kill.
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. Thus, this assessment segment was placed in Category 5b of Iowa’s Integrated Report. [Note: this fish kill impairment was inadvertently omitted from Iowa's 2010 Section 303(d) list of impaired waters but was added to Iowa’s 2012 list.
Results of biological monitoring suggest that Bailey Creek be assessed (evaluated) as "partially supported" based on data collected in 2007, 2011 and 2013 as part of the IDNR/SHL stream REMAP, biocriteria and headwater sampling projects. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species 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 2007 headwater sampling FIBI score was 48 (fair) and the BMIBI score was 56 (good). The 2011 FIBI score was 64 (good) and the BMIBI score was 73 (good). The 2013 FIBI score was 62 (good) and the BMIBI score was 54 (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 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 1994-2004. The riffle habitat FIBI BIC for the 47c ecoregion is 65 and the non-riffle habitat FIBI BIC is 44. The Hess sample/natural substrate BMIBI BIC for the 47c ecoregion is 70. The 2007 sample was located in the 47b ecoregion and the non-riffle habitat FIBI BIC for that region is 32 and the BMIBI BIC is 62. Overall, this segment passed the FIBI BICs 1/3 times and passed the BMIBI BICs 1/3 times in the past seven years.
This aquatic life assessment is now considered "monitored" 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 the recent five-year period to be considered “monitored”.
