Saylorville Reservoir IA 04-UDM-1213

Assessment Comments

Assessment is based on results of monitoring at Saylorville Res. conducted by Iowa State Univ. in 2000-01 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 remain assessed as "fully supported / threatened," and the fish consumption uses remain assessed as "fully supported."  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.  2001and Lutz and Esser 2002).   EXPLANATION:  The Class A (primary contact recreation) uses are assessed as "fully supported."  ISU/ACOE monitoring of levels of indicator bacteria (fecal coliforms) during summers of 2000 and 2001 at mid-lake near the dam and at three locations at each of the two swimming beaches (Sandpiper and Oak Grove) 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 2000-2001 period were as follows:  4 orgs/ 100 ml at the mid-lake station (17 sampling events; max = 140 orgs/100 ml); 7 orgs/100 ml at Oak Grove Beach (16 sampling events; max daily mean = 160 orgs/100 ml); 18 orgs/100 ml at Sandpiper Beach (16 sampling events; max daily mean = 623 orgs/100 ml).   These results indicate full support of the Class A uses.   The Class B(WW) aquatic life uses were assessed as "fully supported / threatened."  Two of the 34 samples from the mid-lake (surface) station during the biennial period exceeded the Class B(WW) WQ criterion for dissolved oxygen of 5.0 mg/l.   These violations occurred on August 24, 2000 (4.98 mg/l) and August 21, 2001 (4.34 mg/l).   According to U.S.  EPA guidelines for Section 305(b) water quality assessments (U.S.  EPA 1997b, page 3-17), the percentage of violations at the mid-lake station (6%) does not suggest a water quality impairment.   No violations occurred for the other Class B(WW) WQ parameters (pH, ammonia) in the approximately 36 samples analyzed for at this station.   Due to violations of the WQ criterion for dissolved oxygen in reservoir surface samples during the 1998-1999 biennial period, the assessment of support of the Class B(WW) aquatic life uses was downgraded from "fully supported" to fully supported / threatened (see assessment for the 2000 report above).   Although this approach is again used for the 2002 report, this change in assessment presumes a minor water quality impact and does not indicate a declining trend in water quality.   Fish contaminant monitoring conducted in Saylorville Reservoir by ISU/ACOE in 2000 and 2001 showed that levels of contaminants (dieldrin, chlordane, alachlor, trifluralin, and chlorpyrifos) in composite samples of whole fish common carp were all less than or equal to ½ of the respective FDA action levels or DNR levels of concern.   The level of dieldrin in the two composite whole-fish samples of common carp from 2001 (189.3 ppb and 110.4 ppb) averaged 150 ppb; this equals ½ of the FDA action level for dieldrin of 300 ppb.   Because this level remains well-below the FDA action level, and because levels of organochlorine contaminants in whole-fish tend to overestimate the levels in fillets, fish consumption uses at Saylorville Reservoir will remain "fully supported."  Additional monitoring is planned for 2002 as part of the ISU/ACOE monitoring network.   For more information on ISU/ACOE water quality monitoring at Saylorville Reservoir, see Lutz et al.  (2001) and Lutz and Esser (2002).