Assessment Comments

Assessment is based on results of (1) USGS ambient water quality monitoring in 2004 and (2) U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2002 and 2004.

Basis for Assessment

SUMMARY:  The Class A (primary contact recreation) uses are "not assessed" due to the lack of water quality information upon which to base an assessment.   The Class B(WW) aquatic life uses are assessed (evaluated) as “fully supporting” based on results of chemical/physical monitoring in 2004.   Fish consumption uses are assessed (monitored) as "fully supported" based on fish contaminant monitoring.   The sources of data for this assessment are (1) the results of USGS chemical/physical water quality monitoring at Keosauqua from March 2004 through September 2004 and (2) results of U.S.  EPA/IDNR fish contaminant monitoring in 2002 and 2004 at Keosauqua.  

EXPLANATION:  The Class A uses were not assessed due to the lack of water quality monitoring and other water quality information for this river segment upon which to assess support of these uses.   Prior to the 2002 report, these uses were assessed based on results of water quality monitoring conducted near Keokuk (see assessments for the 1998 and 2000 reports).   This monitoring station, however, is more than 30 miles downriver from the current assessment segment (IA 04-LDM-0010-3), and previous assessment likely represent an excessive extrapolation of the monitoring results from the Keokuk station.  

The Class B(WW) aquatic life uses were assessed (evaluated) as "fully supported" based on results of water quality monitoring by the U.S.  Geological Survey near Keosauqua in 2004.   No violations of state water quality criteria occurred in the seven samples analyzed for dissolved oxygen, pH, ammonia, chlorpyrifos, DDE, and dieldrin.   Although these results indicate “full support” of the aquatic life uses of this river segment, the number of samples is relatively low and does not meet IDNR guidelines for developing a “monitored” (i.e., higher confidence) assessment.   Thus, the assessment type is considered “evaluated” (lower confidence).

Results of EPA/DNR fish tissue (RAFT) trend monitoring near Keosauqua in 2002 and 2004 showed that  the composite sample of whole-fish common carp collected from this site have low levels of contaminants.   This site has been sampled for whole-fish common carp since 1994 on an every-other-year basis as part of RAFT trend monitoring.   The results from the 2002 sampling show low levels of the primary contaminants (chlordane, PCBs and mercury) in the composite whole-fish sample of common carp:  mercury:  0.101 ppm; total PCBs:  0.135 ppm; and technical chlordane:  0.12 ppm.   The results from the 2004 sampling also show low levels of the primary contaminants (chlordane, PCBs and mercury) in the composite whole-fish sample of common carp:  mercury:  0.062 ppm; total PCBs:  0.136 ppm; and technical chlordane:  0.09 ppm.  

The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes.   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 or 2004 RAFT samplings (or from previous RAFT trend monitoring) conducted in this assessment segment:  the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.