Turkey River IA 01-TRK-152

Assessment Comments

Assessment remains based on results of 2002 IDNR/UHL biological monitoring data: FIBI = 84 (excellent), BMIBI = 71 (good).

Basis for Assessment

[Note:  Prior to the 2008 Section 305(b) cycle, this river 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 remain assessed (evaluated) as "fully supported" based on results of IDNR/UHL biological monitoring in 2002.   Due to age of the most recent fish contaminant data for this segment (greater than ten years), the fish consumption uses are now considered "not assessed."  Note:  USGS collected conducted a single sampling in this segment (near Eldorado; station 05411850) during the 2008-2010 data summary period for the 2012 Integrated Report.   Although no violations of Iowa WQ criteria occurred in this sample.

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

The Class B(WW1) aquatic life assessment was based on data collected in 2002 as part of the IDNR/UHL REMAP 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 84 (excellent) and the BMIBI score was 71 (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 from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The FIBI BIC for this ecoregion is 52 and the BMIBI BIC for this ecoregion is 61.   This assessment is considered evaluated because the drainage area (667 mi2) above this sampling site was greater than the maximum limit (500mi2) that was used to calibrate the Iowa wadeable stream impairment criteria.   Even though this site passed both the FIBI and BMIBI BICs, it is uncertain as to whether or not this segment is meeting the aquatic life criteria because it doesn’t fall in the calibrated watershed size.  

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 2006 and 2010 to be considered “monitored”.   This segment had a single sample collected in 2002.   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).

Due to the age of the data (> 10 years) upon which previous assessments were based, the fish consumption uses for this segment are considered “not assessed.”  Prior to the current (2012) assessment/listing cycle, these uses were assessed (evaluated) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Clermont in 1999.   Because these data are now considered too old (greater than ten years) to characterize current water quality conditions, the fish consumption uses are now considered “not assessed.”