Middle River IA 04-LDM-1086

Assessment Comments

Assessment based on results of (1) IDNR/SHL biological sampling in 1998, 2004 and 2012, (2) U.S. EPA/IDNR fish tissue (RAFT) monitoring at Pammell Park in 2002, and (3) a report of a fish kill in July 2002.

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 in 2007, 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" (IR 3a) due to the lack of information upon which to base an assessment.   The Class B(WW1) aquatic life uses are assessed (evaluated) as "fully supported” (2a) based on results of biological sampling in 1998, 2004 and 2012.   Fish consumption uses are assessed (evaluated) as "fully supported" (IR 2a) based on results of fish contaminant monitoring in 2002.   Sources of data for this assessment include (1) results of IDNR/SHL biological sampling conducted in 1998, 2004 and 2012 as part of the stream biocriteria project, (2) a report of a fish kill on July 20, 2002, and (3) results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring in 2002.  

EXPLANATION:  The Class B(WW1) aquatic life uses are assessed (evaluated) as "fully supported” based on results of IDNR/SHL biological sampling conducted on this stream segment in 1998, 2004 and 2012.   The 1998 FIBI score was 38 (fair) and the BMIBI score was 61 (good).   The 2004 FIBI score was 32 (fair) and the BMIBI score was 53 (fair).   The 2012 FIBI score was 40 (fair) and the BMIBI score was 63 (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 36 and the BMIBI BIC for this ecoregion is 51.   This segment passed the FIBI BIC 2/3 times and passed the BMIBI BIC 3/3 times in the last 15 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 five-year period to be considered “monitored”.   This segment had multiple samples collected in the previous 15 years (1998-2012); however, the multiple samples were not collected during a five-year period.  

A fish kill occurred in this river segment on July 20, 2002 near the Middle River Park south of Winterset.   This kill is believed due to warm water temperatures, low river flow, and the die-off of an algae bloom that reduced levels of dissolved oxygen below that needed to sustain large fish.   At the time of the kill, levels of dissolved oxygen were in the vicinity of 3 mg/l; the water was brownish, probably due to the senescence of the algal bloom.   Because this kill is largely due to natural causes (low flow; high water temperatures), the kill does not influence the assessment of support of the designated aquatic life uses of this stream segment.  

Fish consumption uses remain assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring southwest of Winterset in 2002.   The composite samples of fillets from channel catfish and walleye had low levels of contaminants.   Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.142 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm.   Levels of primary contaminants in the composite sample of walleye fillets were as follows: mercury: 0.184 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm.   These levels of contaminants do not exceed any of Iowa’s advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody and “full support” of the fish consumption uses.