East Fork Des Moines River IA 04-EDM-1793

Assessment Comments

Assessment remains based on 2003 and 2011 IDNR/SHL biological sampling data: FIBI = 45 (fair) & 54 (good), BMIBI = 71 & 72 (both 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, 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) and Class HH (fish consumption) uses remain "not assessed" (IR 3a) due to the lack of information upon which to base an assessment.  

The Class B(WW1) aquatic life uses are assessed (evaluated) as “fully supporting” (IR 2a) based on biological data collected in 2003 and 2011 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 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 FIBI score was 45 (fair) and the BMIBI score was 71 (good).   The 2011 FIBI score was 54 (good) and the BMIBI score was 72 (good).   The aquatic life use support was assessed as fully 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 2/2 times in the last nine years.   The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008.  

This aquatic life assessment is 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 five-year period to be considered “monitored”.   This segment had multiple samples collected in the previous 10 years (2003-2012); however, the multiple samples were not collected during a five-year period.  

Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this assessment segment.