Des Moines River IA 04-UDM-1212

Assessment Comments

Assessment is based on results of monitoring from 2000-02 by (1) Iowa State Univ. as part of the ACOE's Des Moines R. water quality study (including annual fish contaminant monitoring) and (2) IDNR/UHL ambient city monitoring.

Basis for Assessment

SUMMARY:  The Class B(WW) aquatic life uses are assessed (monitored) as "fully supported / threatened" based on results of ambient chemical/physical monitoring from 2000-02.   Fish consumption uses are assessed (monitored) as "fully supported" based on results of annual fish contaminant monitoring during the 2000-02 period.   The assessments of support of the beneficial uses are based on results of (1) water quality and fish contaminant monitoring conducted during the 2000-2002 assessment 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, Lutz and Esser 2002, and Lutz and Cummings 2003) and (2) results of IDNR ambient city monitoring upstream from Des Moines at the Sycamore Access (NW 66th Street; STORET station 10770002) during the 2000-2002 assessment period.  

EXPLANATION:  The Class B(WW) aquatic life uses remain assessed (monitored) 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 66 samples collected at this station during the 2000-2002 assessment period.   In the samples analyzed for toxic metals, the only violations were for mercury:  two of the 10 samples analyzed for dissolved mercury during the 2000-2002 assessment 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 28 samples collected during the 2000-2002 assessment period exceeded Class B(WW) criteria for dissolved oxygen, pH, or ammonia-nitrogen.   None of the 28 samples analyzed for toxic metals (including mercury), and none of the nine 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, 2001, and 2002 showed that levels of contaminants (dieldrin, chlordane, alachlor, trifuluralin, and chlorpyrifos) in composite samples of whole fish common carp (2000, 2001 & 2002) 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 remain assessed as "fully supported."