East Nishnabotna River IA 05-NSH-1816

Assessment Comments

Assessment remains based on results of EPA/IDNR fish contaminant (RAFT) monitoring in 2002 near Red Oak.

Basis for Assessment

[Note:  Prior to the current (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 are "not assessed" due to the lack of information upon which to base an assessment.   The Class B(WW) aquatic life uses remain "not assessed" due to the lack of information upon which to base an assessment.   Fish consumption uses remain assessed (monitored) as "fully supported" based on results of U.S.  EPA/IDNR fish contaminant (RAFT) monitoring near Red Oak in 2002.  

EXPLANATION:  Fish consumption uses remain assessed as "fully supported " based on results of the U.S.  EPA/IDNR fish tissue (RAFT) monitoring near Red Oak in 2000.   The composite samples of fillets from common carp had low levels of contaminants.   Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.095 ppm; total PCBs: 0.165 ppm; and technical chlordane: 0.19 ppm.   [Note:  Typically, samples of both bottom-feeding fish (e.g., common carp) and predator species (e.g., largemouth bass) are collected at RAFT status sites such as the East Nishnabotna River near Red Oak.   Predator species, however, are naturally rare in rivers of southwestern Iowa, and RAFT status samples from these rivers typically contain only the bottom-feeder sample.]

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.   Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa.   In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol.   This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol).   Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses.   This scenario, however, does not apply to the fish contaminant data generated from the 2002 RAFT sampling conducted in this assessment segment:  the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.