Des Moines River IA 04-UDM-1212

Assessment Comments

Assessment is based on results of monitoring in 2000-01 by (1) Iowa State Univ. as part of the ACOE's Des Moines R. water quality study and (2) IDNR ambient city monitoring.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses are assessed as "fully supported / threatened;" fish consumption uses are assessed as "fully supported."  The assessments of support of the beneficial uses are based on results of (1) water quality monitoring conducted during the 2000-2001 biennial period approximately two miles downstream from Saylorville Dam at Sycamore Access (NW 66th Street) by Iowa State University (under contract with the U.S.  Army Corps of Engineers) as part of the Des Moines River Water Quality Study (see Lutz et al.  2001 and Lutz and Esser 2002) and (2) results of IDNR ambient city monitoring upstream from Des Moines at the Sycamore Access (NW 66th Street; station 10770002) during the 2000-2001 biennial period.   EXPLANATION:  The Class B(WW) aquatic life uses remain assessed as "fully supported / threatened."  Results from ISU/ACOE monitoring at the Sycamore Access station show no violations of Class B(WW) water quality criteria for dissolved oxygen, pH, or ammonia-nitrogen in the approximately 44 samples collected at this station during the 2000-2001 biennial period.   In the samples analyzed for toxic metals, the only violations were for mercury:  four of the 10 samples analyzed for dissolved mercury during the 2000-2001 biennial period contained levels of above the Iowa Class B(WW) human health criterion of 0.15 ppb.   None of the 10 samples contained levels of mercury above the Class B(WW) chronic criterion for mercury of 2.1 ppm.   Due, however, to (1) problems with analysis of mercury in water (see pages 3-58 and  3-99 to 3-100 of Iowa's 1996 Section 305(b) report), (2) the historical lack of high levels of mercury in fish tissue samples from this reach of river, and (3) a recent study of mercury levels in the Des Moines River near Des Moines (see assessment for the 2000 report above), data for mercury in water were not used to assess support of the Class B(WW) aquatic life uses of this river reach.   Regardless, the continuing uncertainty regarding the significance of mercury levels in the Des Moines River suggests that the assessment of support of the Class B(WW) aquatic life should remain "fully supported / threatened."  Results from the IDNR city monitoring station at Sycamore Access suggest that the Class B(WW) aquatic life uses are "fully supported."  None of the 14 samples collected during the 2000-2001 biennial period exceeded Class B(WW) criteria for dissolved oxygen, pH, or ammonia-nitrogen.   None of the 14 samples analyzed for toxic metals, and none of the six samples analyzed for pesticides and other toxic organic compounds, exceeded Class B(WW) criteria.   Fish contaminant monitoring conducted downstream from Saylorville Reservoir by ISU/ACOE in 2000 and 2001 showed that levels of contaminants (dieldrin, chlordane, alachlor, trifuluralin, and chlorpyrifos) in composite samples of whole fish common carp (2000 & 2001) and common carp fillets (2001) were all less than ½ of the respective FDA action levels or DNR levels of concern (ISU/ACOE fish tissue samples are not analyzed for mercury).   Thus, fish consumption uses remained assessed as "fully supported."  For more information on ISU/ACOE water quality monitoring in this river reach, see Lutz et al.  (2001) and Lutz and Esser (2002).