Assessment Comments
Assessment is based on 2003 IDNR/UHL REMAP data: FIBI = 50 (fair), 49 (fair); BMIBI = 46 (fair), 42 (fair), 2003 Biocriteria data: FIBI = 60 (good); BMIBI = 78 (excellent) and 2007 IDNR/UHL headwater sampling data: FIBI = 48 (fair), BMIBI = 54 (fair). Riffle habitat FIBI BIC = 65, non-riffle habitat FIBI BIC = 44; natural substrate BMIBI BIC = 70 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 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), 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 (2010) 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" due to the lack of information upon which to base an assessment. The Class B(WW2) aquatic life uses are assessed (monitored) as “partially supporting” based on results of IDNR/UHL biological monitoring conducted in 2003 and 2007 and results of a fish kill investigation in September 2009.
EXPLANATION: The Class B(WW2) aquatic life uses are 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 $8541.66. At the time of this assessment 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 (2007-2009) 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 will be placed in Category 5b of Iowa’s 2010 Integrated Report.
Results of biological monitoring suggest that Bailey Creek be assessed (evaluated) as "partially supported" based on data collected in 2003 and 2007 as part of the IDNR/UHL stream REMAP and biocriteria 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 2003 biocritera riffle habitat FIBI score was 60 (good) and the benthic macroinvertebrate Hess sample (natural substrate) BMIBI score was 78 (excellent). The 2003 REMAP non-riffle habitat FIBI scores were 50 (fair); 49 (fair) and the 2003 benthic macroinvertebrate Hess sample BMIBI scores were 46 (fair) and 42 (fair). The 2007 headwater sampling FIBI score was 48 (fair) 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 2008 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. This segment passed the FIBI BICs 3/4 times and passed the BMIBI BICs 1/4 times in the past six 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 between 2004 and 2008 to be considered “monitored”. This segment had multiple samples collected in the previous six years (2003-2008); however, the multiple samples were not collected during 2004-2008. 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). However, despite this change in assessment methodology and type, this waterbody remains in IR Category 5b and remains on Iowa’s 2010 Section 303(d) list of impaired waters.
