Assessment Comments

Assessment based on 2003 IDNR/UHL stream REMAP biological sampling data: FIBI = 8 (poor), BMIBI = 37 (fair). FIBI BIC = 31; BMIBI BIC = 54.

Basis for Assessment

[Note:  Prior to the current (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, 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 evaluated biological assessment of the Class B(WW1) aquatic life uses was based on data collected in 2003 as part of the IDNR/UHL stream REMAP project.   A series of biological metrics that 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 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 FIBI score was 8 (poor) and the BMIBI score was 37 (fair).  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 from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 31 and the BMIBI BIC for this ecoregion is 54.   This assessment is considered evaluated because the drainage area (1188 mi2) above this sampling site was greater than the maximum limit (500 mi2) that was used to calibrate the Iowa wadeable stream impairment criteria.   Even though this site failed both the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size.