Middle Avery Creek IA 04-LDM-1042

Assessment Comments

Assessment remains based on 2002 IDNR/UHL biological monitoring data: FIBI = 26 (fair), BMIBI = 56 (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 (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 remain "not assessed" due to the lack of information upon which to base an assessment.   The Class B(LR) aquatic life uses remain assessed (evaluated) as "fully supported" based on results of IDNR/UHL biological (REMAP) sampling in 2002.   This assessment is now considered of lower confidence (evaluated) as opposed to higher confidence (monitored) because the data from the 2002 biological sampling are now older than five years, thus, these data are considered less able to accurately characterize current water quality conditions than would be more recent data.  

EXPLANATION:  The Class B(WW2) aquatic life uses remain assessed (evaluated) based on data collected in 2002 as part of the DNR/UHL REMAP 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 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 26 (fair) and the BMIBI score was 56 (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.   This segment passed the FIBI BIC with the aid of the FIBI UAV of 7 points used in assessments that rely on a single (FIBI and/or BMIBI) score.   The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 33 and the BMIBI BIC for this ecoregion is 41.

This aquatic life assessment is considered "evaluated" because there were not two or more samples collected from this segment in multiple years from 2004-2008.   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.