Assessment Comments
Assessment based on the results of Syngenta's Iowa Voluntary Atrazine Monitoring Program from 2000-02.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses and Class B(LW) aquatic life uses remain "not assessed" due to lack of water quality information upon which to base an assessment. The Class C (drinking water) uses are assessed (monitored) as "not supported" due to average levels of atrzine that exceed state water quality standards. The source of data for this assessment is the results of the Iowa Voluntary Atrazine Monitoring Program conducted in 2000, 2001, and 2002 by Syngenta Crop Protection, Inc. (formerly Novartis Crop Protection, Inc.).
EXPLANATION: The Class A and Class B(LW) uses remain "not assessed" due to the lack of recent water quality information upon which to base an assessments. This lake is not part of the ongoing statewide survey of Iowa lakes conducted by Iowa State University. The Class C (drinking water) uses are assessed (monitored) as "not supported " based on results of sampling conducted as part of the Iowa Voluntary Atrazine Monitoring Program conducted in 2000, 2001, and 2002 by Syngenta Crop Protection, Inc..
This monitoring showed that the time-weighted mean levels of atrazine in samples collected from Centerville Reservoir in 2001 (4.11 ug/l) was above the MCL of 3.0 ug/l. The time-weighted mean of atrazine in 2000 (N=30) was 2.64 ug/l, in 2001 (N=31) was 4.11 ug/l, and in 2002 was 1.72 ug/l. Thirty-two of the 48 moving annual averages calculated for the three-year period were above the MCL of 3 ug/l (range: 3.5 to 4.9 ug/l). Based on DNR's Section 305(b) assessment methodology, if the average contaminant level in source water is greater than the MCL, the Class C (drinking water) uses of the source water should be assessed as "not supported."
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring at this lake.
