Assessment Comments
Assessment is based on results of monitoring conducted by Iowa State Univ. as part of the ACOE's Des Moines R./Saylorville Res./Red Rock Res. water quality study.
Basis for Assessment
SUMMARY: Continue to assess support of the Class A (primary contact recreation) uses as "fully supported." The Class B(WW) aquatic life uses were assessed as "fully supported," and the fish consumption uses were assessed as "fully supported." EXPLANATION: The assessments of support of the beneficial uses are based on results of water quality monitoring conducted 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. 1999 and Lutz 2000). ISU/ACOE monitoring of levels of indicator bacteria (fecal coliforms) during summers of 1998 and 1999 at mid-lake near the dam and at three locations at each of the two swimming beaches (North Overlook and Whitebreast) showed that geometric mean levels of indicator bacteria were far below the state water quality criterion of 200 orgs/100 ml. Geometric means for the 1998-99 period were as follows: 4 orgs/ 100 ml at the mid-lake station (18 sampling events; max = 57 orgs/100 ml); 5 orgs/100 ml at North Overlook Beach (17 sampling events; max daily mean = 33 orgs/100 ml); 5 orgs/100 ml at Whitebreast Beach (17 sampling events; max daily mean = 79 orgs/100 ml). None of the combined 120 samples analyzed for fecal coliform bacteria exceeded the 200 orgs/100 ml WQ criterion to protect primary contact recreation uses. The Class B(WW) aquatic life uses were assessed as "fully supported:" none of the 34 samples collected from the mid-lake (surface) station during the biennial period exceeded Class B(WW) WQ criteria for conventional parameters (dissolved oxygen, pH, and ammonia) (samples were not analyzed for toxic metals). Fish contaminant monitoring conducted in Red Rock Reservoir by ISU/ACOE in 1998 and 1999 showed that levels of contaminants (dieldrin, chlordane, alachlor, trifluralin, and chlorpyrifos) in composite samples of whole fish 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 at Red Rock Reservoir, see Lutz et al. (1999) and Lutz (2000).
