Little Cedar River IA 02-CED-576

Assessment Comments

Assessment based on 2002 and 2009 IDNR/UHL biological monitoring data: FIBI = 69 (good) and 80 (excellent); BMIBI = 77, 77 (excellent). Riffle habitat FIBI BIC = 65 and natural substrate BMIBI BIC = 70.

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, 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:  The Class A1 (primary contact recreation) uses remain "not assessed" due to the lack of information upon which to base an assessment.   The Class B(WW1) aquatic life uses are assessed (evaluated) as “fully supported” based on results of IDNR/UHL biocriteria sampling in 2002 and 2009.   Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this river segment.  

EXPLANATION:  The Class B(WW1) aquatic life uses are assessed as “fully supported” based on data collected in 2002 and 2009 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 biocriteria sampling data.   The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were 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 2002 FIBI score was 69 (good) and the BMIBI score was 77 (excellent).   The 2009 FIBI score was 80 (excellent) and the BMIBI score was 77 (excellent).   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 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 this ecoregion is 65 and the natural substrate BMIBI BIC for this ecoregion is 70.   This segment passed the FIBI and BMIBI BICs 2/2 times in the last nine 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 over a five-year period to be considered “monitored”.   This segment had multiple samples collected in the previous nine years (2002-2010); however, the multiple samples were not collected during a five-year period.   Despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.  

Fish consumption uses remain “not assessed” due to the lack of recent fish contaminant monitoring in this river segment.