Assessment Comments

Assessment remains based on 2001 IDNR/UHL biological monitoring data: FIBI = 78, 81 (excellent), and BMIBI = 80 (excellent), 73 (good). Riffle habitat FIBI BIC = 65, 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(LR) aquatic life 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), 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 (2010) assessment, the available water quality monitoring data will be compared to the applicable Class A1 and Class B(WW2) water quality criteria.]

SUMMARY:  The presumptive Class A1 (primary contact recreation) uses are “not assessed” due to a lack of information upon which to base an assessment.   The Class B(WW2) aquatic life uses remain assessed (evaluated) as "fully supported" based on results of IDNR/UHL biological (biocriteria) sampling in 2001.  

EXPLANATION:  The presumptive Class A1 uses are “not assessed” due to a lack of information upon which to base an assessment.  

The Class B(WW2) uses remain assessed (evaluated) as “fully supported.”  This assessment was based on data collected in 2001 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).   Two samples were collected within this stream segment in 2001.   The FIBI scores were 78 (excellent) and 81 (excellent).   The BMIBI scores were 80 (excellent) and 73 (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 1994-2004.   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 2001.

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 2001; however, the multiple samples were not collected during 2004-2008 and/or were not collected in multiple years.   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).   Despite this change in assessment methodology and type, this waterbody remains in IR Category 2a.