Assessment Comments
Assessment is based on 1997 and 2003 IDNR/UHL biocriteria sampling data: FIBI = 29 & 45 (fair), BMIBI = 42 (fair) & 72 (good). Non-riffle FIBI BIC = 32; BMIBI BIC = 62.
Basis for Assessment
[Note: Prior to the 2008 Section 305(b) cycle, this stream segment was designated only for Class B(WW) aquatic life uses, including fish consumption 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), and due to the completion of a Use Attainability Analysis in 2007, this segment is also now designated for Class A1 (primary contact recreation) uses. This segment remains designated for warmwater aquatic life use (now termed Class B(WW1) uses), and for fish consumption uses (now termed Class HH (human health/fish consumption uses).]
SUMMARY/EXPLANATION: The Class A1 (primary contact recreation) uses are "not assessed" due to the lack of information upon which to base an assessment.
The assessment of the Class B(WW1) aquatic life assessment was based on data collected in 1997 and 2003 as part of the IDNR/UHL stream biocriteria project. 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 1997 FIBI score was 29 (fair) and the BMIBI score was 42 (fair). The 2003 FIBI score was 45 (fair) and the BMIBI score was 72 (good). The aquatic life use support was assessed as partially supporting (=FS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports. The non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62. This segment passed the FIBI and BMIBI BICs 1/2 times in the last 12 years. The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.
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 12 years (1997-2008); however, the multiple samples were not collected during 2004-2008. Additionally, 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).
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this assessment segment.
