West Nishnabotna River IA 05-NSH-1444

Assessment Comments

Assessment is based on results of U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2011.

Basis for Assessment

[Note:  Prior to the 2008 Section 305(b) cycle, this stream 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 (see http://www.iowadnr.com/water/standards/files/06mar_swc.pdf), 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 and the Class B(WW1) aquatic life uses both remain "not assessed" due to the lack of information upon which to base an assessment.   The fish consumption uses remain assessed (evaluated) as "fully supported" based on results of U.S.  EPA / IDNR fish tissue (RAFT) monitoring near Harlan in August 2011.  

EXPLANATION:  Fish consumption uses remain assessed (evaluated) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring near Harlan in 2011.   The composite samples of fillets from channel catfish had low levels of contaminants.   The composite samples of fillets from channel catfish had very low levels of contaminants.   Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.028 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm.   The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses.   The fish contaminant data generated from the 2011 RAFT sampling conducted in this segment of the West Nishnabotna River indicate that the 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.