Des Moines River IA 04-LDM-1003

Assessment Comments

Assessment is based on (1) results of IDNR ambient monthly monitoring near Keokuk and (2) fish tissue monitoring near Croton. See attached document for details.

Basis for Assessment

SUMMARY:  Continued to assess support of both the Class A (primary contact recreation) uses and the Class B(WW) aquatic life uses as "fully supported / threatened."  Based on results of EPA/DNR (RAFT) fish tissue monitoring, fish consumption uses were assessed as "fully supported/threatened."  EXPLANATION:  The assessments of the Class A and Class B(WW) uses are those developed for the 1998 report; these assessments were based on results of the two years of DNR quarterly monitoring (1996-1997) on the Des Moines River at Keokuk (see assessment for the 1998 report above).   Results of EPA/DNR fish tissue (RAFT) trend monitoring near Keosauqua in 1998 showed that levels of technical chlordane in whole-fish common carp (0.29 ppm) were just below the U.S.  FDA action level of 0.30 ppm.   Although levels of organochlorine contaminants in whole-fish samples tend to overestimate levels in the edible portion of the fish, this level of chlordane suggest that levels in edible portions may be greater than ½ of the FDA action level for chlordane.   Thus, according to DNR's assessment methodology, the fish consumption uses should be assessed as FST.   In addition, results of RAFT (fish tissue) status monitoring in 1999 showed that levels of all contaminants in fillet samples from common carp and freshwater drum collected from the Des Moines River near Croton were well below ½ of the respective FDA action levels as well as DNR levels of concern.   Due to recent expansion of the DNR WQ monitoring network, monthly monitoring began at the Keokuk station in October 1999; more adequate data will be available for assessing the aquatic life and primary contact uses at this station for the 2002 report.