Chequest Creek IA 04-LDM-1030

Assessment Comments

Assessment based on 2003 and 2011 IDNR/SHL biological sampling data: FIBI = 35, 45 (fair), BMIBI = 44 (fair), 59 (good). FIBI BIC = 33; BMIBI BIC = 41.

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, 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 assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]

SUMMARY/EXPLANATION:  The presumptive Class A1 (primary contact recreation) uses remain "not assessed" (IR 3a) due to the lack of information upon which to base an assessment.  

The Class B(WW2) aquatic life uses are assessed (evaluated) as "fully supported" (IR 2a) based on results of 2003 and 2010 biological sampling conducted as part of the IDNR/SHL stream biocriteria project.   The 2010 FIBI score was 35 (fair) and the BMIBI score was 44 (fair).   The 2003 FIBI score was 45 (fair) and the BMIBI score was 59 (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 biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008.   The FIBI BIC for this ecoregion is 33 and the BMIBI BIC for this ecoregion is 41.   This segment passed the FIBI and BMIBI BICs 2/2 times in the past 10 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 recent 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 2008-2012.   Despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.