Assessment Comments
Assessment is based on results of ambient water quality and fish tissue monitoring and fish kill reporting conducted by Iowa State University as part of the ACOE's Des Moines R./Saylorville Reservoir/Red Rock Reservoir water quality study.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses are assessed (monitored) as "fully supporting" based on results of routine monitoring for indicator bacteria. The Class B(WW) aquatic life uses remain assessed (monitored) as "not supported," due to repeated fish kills downriver from Red Rock Dam. The fish consumption uses remain assessed (monitored) as "fully supported" based on results of fish contaminant monitoring in 2000, 2001, and 2002. The assessments of support of the beneficial uses are based on results of water quality monitoring and fish kill reporting conducted during the 2000-2002 assessment period 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).
EXPLANATION: Class A uses were assessed (monitored) as "fully supported" based on results of ambient water quality monitoring from the ISU/ACOE station 0.7 mi downstream from Red Rock Dam. For purposes of Section 305(b) assessments, DNR uses the long-term average monthly flow plus one standard deviation of this average to identify river flows that are materially affected by surface runoff. According to the Iowa Water Quality Standards (IAC 1990:8), the water quality criterion for fecal coliform bacteria (200 orgs/100 ml) does not apply "when the waters are materially affected by surface runoff." Twenty-four of the 26 samples collected from the ISU/ACOE station during the 2000, 2001, and 2002 recreational seasons were collected at flows not materially affected by surface runoff. This monitoring showed that (1) geometric means for fecal coliform (indicator) bacteria in summer periods of 2000, 2001, and 2002 were well below the state WQ criterion of 200 organisms/100 ml and (2) no samples exceeded the U.S. EPA-recommended single sample maximum value for fecal coliforms (400 orgs/100 ml). At this monitoring station, the geometric mean of the 24 non-runoff-affected samples collected during summers of 2000 and 2001 was 24 orgs/100 ml, with no samples exceeding the 400 organism/100 ml single sample maximum. These results indicate extremely low levels of indicator bacteria in this reach of river. According to U.S. EPA guidelines for Section 305(b) reporting, if geometric means for fecal coliforms are less than 200 organisms/100 ml, and if less than 10% of samples exceed 400 orgs/100 ml, the primary contact recreation uses are "fully supported" (see pgs 3-33 to 3-35of U.S. EPA 1997b).
Results from this ISU/ACOE monitoring station also suggest that the Class B(WW) aquatic life uses are "fully supported/threatened"; however, the Class B(WW) aquatic life uses remained assessed as "not supported" due to repeated fish kills in this river segment. No violations of Class B(WW) water quality criteria for conventional parameters (dissolved oxygen, pH, ammonia-nitrogen) occurred in the 66 samples collected at this station during the 2000-2002 assessment period. In the 12 samples analyzed for toxic metals, the only violations were for mercury: although none of the 10 samples contained levels of mercury above the Class B(WW) criterion of 2.1 ug/l, five of the ten samples contained levels of dissolved mercury above the Iowa WQ criterion for human health (fish) of 0.15 ug/l. According to U.S. EPA guidelines for Section 305(b) reporting (U.S. EPA 1997b, page 3-18), more than one violation of a water quality criterion for a toxic contaminant within a three-year period indicates that the aquatic life uses are not fully supported. 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 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." Two fish kills were reported for this river reach during the 2000-2002 assessment period. These kills occurred on May 24, 2000 and August 14, 2001 immediately downriver from Red Rock Dam. Both kills were relatively minor and involved channel catfish, freshwater drum and/or white bass. Fish killed in both events exhibited signs of gas bubble trauma (see Lutz et al. 2001:175 and Lutz and Esser 2002:207). According to DNR's assessment methodology for Section 305(b) reporting, occurrence of more than one fish kill during the most recent three-year period suggests that the aquatic life uses are "not supported." Thus, the Class B(WW) aquatic life uses of this river reach remained assessed as "not supported" due to repeated fish kills.
Fish contaminant monitoring conducted downstream from Red Rock 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 and fillets of common carp were all less than ½ of the respective FDA action levels or DNR levels of concern. Thus, fish consumption uses were assessed as "fully supported." For more information on ISU/ACOE water quality monitoring in this river reach, see Lutz et al. (2001), Lutz and Esser (2002), and Lutz and Cummings (2003).
