ADBNet

Assessment Comments

Assessment based 2011 and 2013 IDNR/SHL biological sampling data: FIBI = 59, 65 (good); BMIBI = 64, 65 (good). FIBI BIC = 52, BMIBI BIC = 61.

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:  The 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 (monitored) as "fully supporting" (IR 2a) based on results of IDNR/SHL biological sampling conducted in 2011 and 2013.  

EXPLANATION:  The Class A1 (primary contact recreation) uses are "not assessed" due to the lack of data for indicator bacteria upon which to base an assessment.  

The Class B(WW2) aquatic life uses are assessed (monitored) as “fully supporting” based on data collected in 2011 and 2013 as part of the IDNR/SHL follow-up sampling 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 2011 FIBI score was 59 (good) and the BMIBI score was 64 (good).   The 2013 FIBI score was 65 (good) and the BMIBI score was 65 (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 52 and the BMIBI BIC for this ecoregion is 61.   This segment passed the FIBI BIC 2/2 times and passed the BMIBI BIC 2/2 times in the last three years.   This aquatic life assessment is now considered "monitored" 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 in a recent five year period to be considered “monitored”.     This segment had multiple samples collected in the previous three years (2011-2013).