Assessment Comments
Assessment is based on results of the Iowa Voluntary Atrazine Monitoring Program in 2000 & 2001.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses and the Class B(LW) aquatic life uses remain "not assessed." The Class C (drinking water) uses are assessed (monitored) as "fully supported / threatened." Fish consumption uses remain "not assessed." The source of data for this assessment is the results of the Iowa Voluntary Atrazine Monitoring Program conducted in 2000 and 2001 by Syngenta Crop Protection, Inc. (formerly Novartis Crop Protection, Inc.). EXPLANATION: The Class A and Class B(WW) uses remain "not assessed" due to the lack of water quality information for this lake. The assessment of support of the Class C (drinking water) uses was based on the results of the Syngenta "Iowa Voluntary Atrazine Monitoring Program" in 2000 and 2001 (only seven samples were collected in 1999; none of these values exceeded the MCL for atrazine of 3 ug/l). This monitoring showed that the time-weighted mean levels of atrazine in samples collected from Loch Ayr in both calendar years 2000 and 2001 were below the MCL of 3 ug/l. The time-weighted mean of atrazine in 2000 (N=31) was 1.65 ug/l and in 2001 (N=29) was 2.94 ug/l. Yearly maximum values were 2.2 ug/l in 2000 and 7.2 ug/l in 2001. None of the 31 samples collected in 2000 exceeded the MCL; 13 of the 29 samples collected in 2001 did exceed the MCL. Based on DNR's Section 305(b) assessment methodology, if the average contaminant level in source water is less than the MCL, but the MCL is exceeded in one or more samples, the Class C (drinking water) uses of the source water should be assessed as "fully supported / threatened." Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring at this lake.
