Assessment Comments
Assessement is based on fish tissue (RAFT) monitoring in 1997, 1999, & 2001.
Basis for Assessment
SUMMARY: Continued to use the assessment of support of the Class A (primary contact recreation) uses developed for the 1998 report ("partially supported"). Due to the lack of water quality monitoring information, continued to consider the Class B(WW) aquatic life uses as "not assessed." Fish consumption uses remain assessed as "fully supported/threatened. EXPLANATION: The assessment of the Class A primary contact uses remains based on observations of combined sewer overflows to the Des Moines River by DNR staff in June 1995 (see above assessment for the 1996 report). That is, the contributions of the combined sewer overflows would likely cause elevated levels of indicator bacteria in this reach of the Des Moines River. The Class B(WW) aquatic life uses remain "not assessed" due to the lack of recent water quality information upon which to base an assessment. The DNR quarterly monitoring station at Ottumwa was last monitored in 1992 and 1993; these data are considered too old (greater than five years) for determining current water quality conditions. Due to recent expansion of the DNR WQ monitoring network, monthly monitoring began at the Ottumwa station in October 1999. Data from this monitoring will enable development of an updated assessment for the Class A uses and an assessment of the Class B(WW) aquatic life uses for the 2002 report. Fish consumption uses remain assessed as FST. As noted above, results of EPA/DNR (RAFT) fish tissue monitoring in 1997 showed that the level of technical chlordane in the sample of common carp fillets (0.22 ppm) was greater than one-half the FDA action level (0.30 ppm). Due to sampling difficulties, a complete sample was not obtained for RAFT follow-up monitoring in 1999. The partial sample of channel catfish fillets, however, contained 0.29 ppm of technical chlordane; this level is just below the FDA action level of 0.300 ppm. Based on DNR's assessment methodology, these contaminant levels suggest that fish consumption uses should be assessed as "fully supported/threatened." Additional fish tissue monitoring will be conducted for the 2001 RAFT to better determine levels of chlordane in the bottom-feeding fish of this river reach.
